I notice that the ⌘? shortcut to the User’s Guide (TaskPaper > Help > User's Guide) in the build that I’m using (Version 3.8.11 Preview (428)) still points to an older URL, which Safari now responds to with an invalid certificate warning.
I’ve remapped that key here to the current URL:
https://www.taskpaper.com/guide
Using Keyboard Maestro:
( I imagine that any newer TaskPaper builds will be moving towards that remapping already )