Temporary file not found when opening an HMI project

Why does the software report a temporary file was not found?

The message means the software launched fine, then failed to create or find its scratch .tmp file in the Windows temporary directory while opening the project; the causes to check are a crowded temp folder, insufficient rights, security software or UAC blocking access, or a path over 260 characters.

The launch works, so the installation is intact. The failure lands one step later, when the program writes a scratch .tmp file into its Windows temporary folder and reads the project against it. When that write is denied, crowded out or handed a path Windows refuses, you get exactly this message.

Check five causes, in this order:

• A crowded temporary folder. Years of leftovers fill the drive or the folder, and the new scratch file has nowhere to go.
• Insufficient user rights. The signed-in account cannot write to and delete from the folder.
• Security software. Protection sees a program dropping files into Temp and blocks the write, often without a prompt.
• UAC. Windows stands between the program and the folder and refuses or redirects the write.
• A temporary path too long. The full path, down to the scratch file name, runs past the 260-character Windows limit.

One detail in the message matters for the checks that follow: it prints the path shortened with an ellipsis, so read the real folder location from Windows, never from the message.

Is the project file corrupt, or is it this laptop?

Run two tests before you blame the file: open a known-good project on this laptop, and open the problem project on another PC; which one fails tells you where the fault lives.

Copy, never move: test on duplicates so the original stays untouched. Run both tests when a second machine is available; when it is not, carry on with the laptop checks, which need nothing extra.

When the second machine rejects the file as well, recovering a corrupt project file after a crash walks the backup-and-recovery sequence before you rebuild anything. When the trouble began the day the project landed on this newer Windows laptop, project transfer failing on a newer Windows PC covers the version and driver side of that move.

How do you find the real temporary folder and check its free space?

The error text shortens the path with an ellipsis, so read the real folder from Windows: open the user temporary directory shown in your TEMP variable and check free space on that drive before you change anything.

Windows keeps one temporary directory per account. Its exact location lives in that account's TEMP and TMP environment variables, and on an unmodified machine it is a Temp folder inside the user profile. Open the folder from that path in File Explorer, then right-click the drive, choose Properties and read the free space.

A scratch write needs room to create, grow and delete files. If Properties shows almost nothing free, say 900 MB free of a 237 GB drive, a failed scratch write is what a full volume produces, and the cleanup in the next section is the move. Write the number down; you will compare against it after cleanup.

What can you safely delete from the temporary folder?

Close the HMI software and every other running program first, then clear stale temporary files with Windows' built-in Disk Cleanup tool; delete only files Windows reports as unused, and leave anything flagged as in use strictly alone.

1. Close the HMI software and every other running program, so nothing holds a file open.
2. Open the temporary folder from the TEMP path.
3. Run Disk Cleanup from the Start menu, or delete the stale files directly from that folder.
4. Leave anything Windows flags as in use alone, and touch nothing outside the temporary folder.
5. Reopen the software and open the same project.
6. Compare the free space with the number you wrote down.

If the project now opens, the crowded folder was the cause, and a scheduled monthly cleanup keeps it that way. If the drive fills again within days, something is retaining files on purpose: the article on an HMI log drive that keeps filling shows how to work out which files are oldest and whether rollover is set. If the error survives a cleanup with gigabytes free, go count the path.

What does a worked example of the 260-character path limit look like?

Windows caps a whole path at 260 characters, and the software's scratch name rides on top of your TEMP folder, so count the full string before you call the path too long; the worked example below shows the arithmetic.

Windows documents the ceiling as MAX_PATH, 260 characters for a complete path string, and the scratch name sits at the end of your TEMP path, so the complete string is what has to fit.

Scenario: a standard user profile, TEMP set to C:\Users\bsmith\AppData\Local\Temp, and an error shape whose subfolder carries an eight-digit code in parentheses. The subfolder and file names below are example inputs; count yours from the folder, since the message shortens the path.

34 + 24 + 13 = 71 characters, which leaves 189 characters of headroom under the 260 limit. On this laptop the path is ruled out; the cause is space or access. The decision number works in both directions: the subfolder and file pieces add 37 characters, so the TEMP base would have to run past 223 characters (260 - 37) before the limit bites. A redirected TEMP such as D:\Projects\Line 12\Controls\HMI Work\Scratch counts 45 characters and totals 82, still far short.

If your own count crosses 260, move the account's TEMP and TMP variables to a short folder such as C:\Temp, sign out and back in, and retest; the variables are a supported Windows setting. The same ceiling explains failures elsewhere: files that sit close to the limit break when a program derives new paths underneath them, which is why very long project names produce save and copy errors in synced folders.

Do rights, UAC or security software block the temporary folder?

If the folder has space, a short path and still fails, test whether your user can actually write there: create a text file in the temp folder and delete it; when that fails, a permission, a UAC prompt or security software is blocking the write.

The create-and-delete test settles write access in under a minute. In the temporary folder, create a new text document, rename it, then delete it.

For a rights result, identify and stop there: the Windows administrator reviews the folder's permissions and ownership and grants the specific rights the account needs. Leave the drive's broader permissions as they are; an open temp folder is a favorite malware drop point.

For a software-side result, open the protection software's log and look at the exact minute of the failed open; blocked actions are recorded. The correction that lasts is a narrowly scoped exception for this software's temporary folder, added by the administrator and verified with the same create-and-delete test. UAC gets the same treatment: an administrator-approved temporary test isolates it, and the durable fix is a rule, never protection left switched off.

Running the software as administrator is a one-open diagnostic: if elevation lets the project open, an access rule is the block. Leave it there; the rule is still broken tomorrow.

When do you stop and hand this to the Windows administrator?

Stop and hand the laptop to your Windows administrator before you change security policy, disable protection, delete files flagged as in use, or touch the only copy of the project; bring the exact error text, the full temp path and your two swap-test results.

One safety rule covers the whole job: test on copies, so a wrong move costs a duplicate and never the original.

Hand over a package the administrator can act on:

• The exact error text, with the software name and version.
• The TEMP path and its character count from the worked example.
• Both swap-test results.
• Free space before and after cleanup.
• The create-and-delete test result.
• Any protection-software log entries at the minute of failure.

Recommendation: Run the two-file swap test first, always. If a known-good project also fails on this laptop, clean the temporary folder, count the TEMP path against the 260-character limit using the 223-character base rule, then have the administrator check rights, UAC and security software, in that order. Call the project file corrupt only once it fails on two machines.

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