When the Contents tab opens but every topic page shows Action cancelled, the replaced help file is blocked or misplaced and the software is fine. Match the file to the installed release, click Unblock on the file's General properties tab, and keep the file on the workstation's local drive rather than on a network share.
You replaced the help file for your HMI programming software, and now every topic page shows the browser's Action cancelled page while the Contents tab still lists every section. The software is not broken. The new file is blocked, misplaced, or the wrong release, and a reinstall usually copies the same fault straight back. This fault sits on the Windows side of the engineering workstation, like dialog text clipped by legacy Windows fonts, so the shop-floor screens themselves need nothing here. The repair is a release and size check, the documented Unblock step on the file's properties sheet, and a local copy: about 10 minutes once you have the correct package downloaded.
What the symptoms point to
The failed topic page prints one of two strings: Action cancelled, or Navigation to the webpage was canceled. Both are the same block, so match your symptom to its cause before changing anything:
- Contents opens, every topic fails. The viewer reads the file's index but refuses to render topic pages. One shared cause is at work: a download mark on the file, a network-share location, or a release mismatch.
- Topics fail when you open the .chm on its own. The file or its location is the problem. Check the download mark and the path first.
- Topics open standalone but fail from inside the software. The software is opening a different file, or an old path. Compare the two locations and repoint the software.
- One topic fails while its neighbours open. That entry's content is at fault, not the package. Compare the failing entry with a working one before you replace anything.
- Help is missing after the upgrade, or the help folder looks thin. The copy is incomplete. It is the same pattern as a project transfer that drops a firmware file: the procedure finishes, the file never arrives.
Check the release match before anything else
Open the software's version information and write down the installed release. Compare it with the release the help package names on its download page or in its instructions. Then check three placements: the file sits in the folder the instructions name, the old file was overwritten by the intended file, and what landed is the help file itself, not an archive or an installer left in place. If the release or the folder does not match, fetch the matching package from the software vendor and place it as the instructions say. Overwriting again by guesswork buries the fault under a second one.
Unblock the file Windows marked as a download
Windows flags every file that arrives through a browser, and the help viewer applies an internet-zone check to flagged files: it draws the contents tree but declines to paint topic pages. The documented fix sits on the file itself. In Windows Explorer, right-click the .chm file, choose Properties, and on the General tab click Unblock, then OK. Microsoft documents this procedure for compiled help files in knowledge base article KB896054. Reopen the help and open a few topics before you touch anything else.
Do not loosen browser security or trusted-site settings to make help render. On a managed workstation, that decision belongs to the administrator. The same properties-sheet step clears blocked downloads elsewhere in industrial software; the troubleshooting steps for blocked downloads apply it to installer packages that refuse to run.
Keep the help file on a local drive
Windows treats a UNC network path as internet-zone content for help, exactly as it treats a download. A file that renders from a folder on the C: drive can fail from \\server\\share\\, with an identical error page. Copy the .chm to a local folder, use the folder the help instructions name, and open help from there. With the file local, a blocked topic page has one remaining cause, the download mark, and Unblock is the whole fix.
Example: the 1.2 MB file that could never work
Suppose the download page lists the help file at 14 MB, one of three files totalling 21 MB. After the upgrade, the help folder on the file server holds a .chm of 1.2 MB. The listing says 14 MB, and 1.2 / 14 = 0.086, so the folder copy is about 9 percent of the real file: a stub, or a transfer that stopped partway. That file cannot render a topic page no matter what else you fix.
Recopy the package to a folder on the workstation's C: drive. The folder now shows 14 MB, matching the listing. Right-click the file, Properties, General tab: Unblock is there, because the file came through the browser. Click Unblock, then OK. Reopen the software and open five topics from Contents. All five render topic text, and they render again after one close-and-reopen of the software.
The decision: the fault was an incomplete copy sitting on a network share, plus a download mark on the replacement. A recopy to a local path and one Unblock click fixed it. The installation was never touched and no security setting changed.
Reinstall last, and only once
A reinstall that pulls the same package from the same share reproduces the same page, and it rewrites a working installation when only the help content is affected. Keep the installer and the help package before you start. Use the vendor's documented repair or reinstall only when the help file is missing or damaged beyond what the package's own instructions restore, and install the software and its help in the documented order and destination. Afterwards, open the topics that failed before the repair, not just one. If Action cancelled returns after a clean reinstall, stop repeating it: the file is still marked or still on the share, and another reinstall clears neither.
What to do, in order
- Record the installed release and compare it with the help package's release.
- Compare the copied file's size in MB with the size on the download page.
- Copy the file to the documented folder on the workstation's local drive.
- Right-click the file, Properties, General tab, Unblock, OK.
- Reopen the software and open five topics, then repeat the check after one close-and-reopen.
- Reinstall only if step 1 or step 2 found a mismatch, and retest the same five topics afterwards.
Recommendation: Check the release and the file size before anything else; when the file is the right one, Unblock plus a local path is the whole repair. Reinstall only when the version or the size does not match, and stop at the first repeat of the same page, because a reinstall cannot strip a download mark or turn a share into a local drive.
Questions
There is no Unblock button on the file's properties sheet. What now?
No button means Windows did not flag this file as an internet download, so the block lies somewhere else. Return to the two checks that leave visible traces: the file's size against the size on the download page, and the file's path, because a network share gets the same treatment as a downloaded file. Move the file to a local folder and retest before changing any system security setting.
Why does the Contents tab still work when every topic page is blocked?
The index is a list the viewer reads directly from the help file, but each topic page is painted through the viewer's embedded browser, and that painting step is where the downloaded-file check applies. A marked file can show a complete contents tree and still refuse to display a single topic page.
Does the Action cancelled page mean the HMI software installation is damaged?
Test one function that does not open help, such as loading a project in the editor. If it behaves normally, the application is intact and the fault is confined to help content. Treat a full reinstall as the last step, after the version, size, Unblock and local-path checks, because the reinstall copies the same file back to the same place.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.