Hi there!
Yes, you can’t open a new tab or new browser with the same app link. We have blocked the editing of applications in multiple tabs/browsers/by different people, as it could lead to progress not being saved.
Users will also be marked inactive if they have an idle tab for more than an hour. If you see this in a previously inactive tab, you can reload your tab and it should work (if there are no other instances open).
Please check all your tabs and windows for any idle window! If you have collaborators, you should check with them too.