Was there a recent update to Teams that broke Forms again? In Teams, Forms for the shared document library won't open in the side panel, they go full page. They open correctly in the panel in SharePoint Online however.
I'm using app version 184.108.40.206 and tried both the new Forms designer 3.1.6 and the old designer 2.0.7. I've cleared cache and republished my forms. Teams Version is Windows 64bit 1.6.00.22281.
Also, my Forms won't open at all (Panel or full page) in the new Teams preview, version 23202.1509.2295.2283, they just show a blank page.
I've been using Forms for 5+ years and this issue has happened a couple times before, usually you guys roll out a fix within a day or two. But if nobody else is reporting this issue, it must be me! That, or nobody uses Forms within Teams? I've tested this on 2 Win64 PCs and MacOS, same behavior on all 3. The videos you requested are attached. Note that always give plenty of time for the code to load so the panel should open instead of the full page.
My Teams client: You have Microsoft Teams Version 1.6.00.22281 (64-bit). It was last updated on 8/14/2023.
And yes, the other version is Teams Public Preview.
Thank you for bringing this to our attention! We were not able to reproduce the second part of the request (Forms are not open at all), if you have any additional information - please, let us know!
As for the first part related to Document libraries, we won't be able to fix it due to MS Teams limitations - it has its own rendering mechanism specifically for document libraries which sadly doesn't support customizers.