I notice that Daryl_Anderson found that deleting “%APPDATA%\MongoDB Compass Community” fixed his issue. I found something related to that in that I eventually found a log statement that mentioned a JSON error that was in a comparable directory.
So I used ProcMon from SysInternals to capture process activity for the Compass process at startup. In the ProcMon output, the last file mentioned after startup was “%AppData%\MongoDB Compass\AppPreferences\General.JSON”.
Opening that file revelaled JSON that was obviously malformed, with the following item added outside the outer closing brace of the rest of the values - attached is a diff versus the General.json preferences from a colleague
Temporarily deleting the corrupt portion allowed Compass to start fully (and obviously I kept my previous saved connections as I had not deleted other %APPDATA% files where those are saved).
Maybe one for the Compass development team, to check for malformed JSON on these files at startup?
