When Opening Scene there is a startup script error.
Anvil embeds reference to a script in your 3ds Max scripts folder. If that file is missing, there can be an error.
Anvil embeds a reference to load a file at this location into your scene's startup scripts directive:
If that file does not exist, there can be a startup error when opening the file. Wall Worm 2.294+ no longer links to that file directly but has an inline script to see if the file exists, alleviating the problem.
To fix this in existing files where the file does not exist, you can download and install this patch script: WW Legacy Startup Patch
Other solutions are to Open Anvil once after the scene loads and then resave the file. If Wall Worm is no longer installed, you can run this code in the MAXScript listener: