I'm also having issues with the new Companion App. I was editing an excel file
Once I click the Update button the on the browser, I see a message the file was uploaded. The excel file stays open, but the update button in the browser goes away.
If any changes are subsequently made in the open excel doc, I see a message the changes were saved in confluence - but they are NOT saved! This is a terrible user experience and will cause many users to lose information. I can't roll this out to my team, as I know they will miss the step and lose their information.
I also used to be able to re-open documents from confluence directly in excel recent file list. This was an incredibly useful ability and allowed me to work naturally. This ability seems to be gone too. I am really considering a move to AirTable or Google docs because the attachment capabilities in Confluence are going backwards not forwards.
