Same problem on both 32-bit and 64-bit Office. Tried on several computers.
Outlook version 1902
Tried several client versions, latest I found was 188.8.131.525 (also identified ad 12.3.9717).
Add-in is loaded.
Path is defined ok.
Tried running ResetEVClient.
To be clean, I am able to open archived emails. But I don't have the menu in Outlook for EV, where you can unarchive mail etc.
Usually, this indicates that the mailbox is not enabled for archiving. Can you verify that? also try to run a sync on the task handling this mailbox, for that mailbox specifically. See if that works.
Which Outlook? If you use the 'click to run' version, you need the 12.4 client. That can only be downloaded if you have support and maintenance in your contract. You should have had a message mid/end december, as 12.4 was released on december 3.