Diarium version: 188.8.131.52
OS + version: Windows 11 v21H2 (Build 22000.376)
Diarium was working perfectly on both of my computers until the Microsoft Store installed the latest update (v184.108.40.206).
After the update, Diarium crashed, on both computers, immediately after opening.
This was cured by uninstalling the app, rebooting and re-installing from the Store.
Although this cured the program crashes, there were problems with Cloud Sync when using Dropbox. Dropbox repeatedly requested authorisation. I "Reset login credentials" several times but this did not fix the issue.
I then switched to OneDrive for Cloud Sync and this worked perfectly!
I am happy to continue using OneDrive but thought that you might wish to investigate further.
Note that I use two factor authentication on both accounts (codes from Google Authenticator).