Outlook 2019 not sending emails and getting "not implemented" when trying to create new calendar events

Question

For the past 4 months now, or remote users have been encountering a frustrating issue that we have not been able to nail down. It is happening mostly with users on laptops who work remotely, not on our desktops permanently in the office. We have Office 2019 and many of our users have been experiencing issues in Outlook such as: not being able to send emails but they can receive them, and getting the "not implemented" error when trying to create a new calendar event. Also at the same time they are unable to open any Excel or Word documents. They receive no errors, the documents just don't open. We can temporarily fix the issue by going into the registry and changing the "users" permission on the SecurityManager to allow all or full control. Then when windows does another update, it resets this key and we again have to go in and modify the registry key again. This has been happening repeatedly for nearly 60 users for the past 4 months. I've gone so far as to try calling Microsoft and opening a ticket but because my work email is my two factor authentication method for my personal account, they will not address my issues with as a work issue.... it kicks me to a "home user" and no one will assist and the auto attendant hangs up on me. I am desperate for any help with this issue.

Things we have tried:

Running a repair on the OST and PST (despite the issue causing issues in more than just outlook)

Running windows and dell/HP updates

Creating new OST files by creating new Profiles for Outlook

Running a repair on the Windows

Disabling Office updates (to see if that would stop the resetting of this key)

Monitoring and removing updates pushed out through our WSUS that may be causing the reset on the registry key (no luck)

Making sure that anyone working remotely is first connected to our VPN before opening any Office 2019 apps

Updating our VPN application

Making sure that users are not connected to metered wifi or cabled networks

Any assistance would be greatly appreciated!