After installing Windows 10 update 21H2 and KB5007289 I rebooted and I was unable to get into my company file. It sometimes displays a COM error but it mostly just closes out the application. The event view logs Event ID 4 - An unexpected error has occurred in QuickBooks: Premier Professional Services Edition 2020 QuickBooks has experienced a problem and must be shut down, ErrorCode:1998304546. 

Things I've tried so far to fix this:

- QuickBooks Tool Hub: Program Quick Repair, Diagnostics, File Doctor

- Reinstalled QB and ran updates. 

- Removed W10 21H2 and KB5007289 updates. 

- Disabled Antivirus and added exclusions.

I'm also seeing this error in the event logs:  

An unexpected error has occurred in "QuickBooks: Premier Professional Services Edition 2020":
DBConnPool::HandleConnectionError errorCode:-6069, dbCode:-103 from file:'src\connpool.cpp' at line 1042 from function:'DBMgr::DBConnPool::init'

When I reinstalled the application was stable and I was able to login to the database. As soon as I applied the latest updates the program started crashing again. All other actions above had no effect.

Please let me know your ideas. Thanks!