Issue adding (Static) Tab app to group call

[pugelarouge]

TLDR : Adding a simple Static tab app to a group call randomly fails for some attendees.

We have identified an issue by which adding a tab app during a group call / meeting is failing for some attendees.

It does not seem to relate to if the attendee is in-tenant or from another tenant.

The app is a 'made for my organisation' app (I.E. manifest.zip uploaded to tenant admin rather than from store or side loaded).

We initially identified the issue when adding the app / tab to chat programmatically from a bot, however we have reduced this down to a manifest and a static webpage, and adding this manually still have the same issue.

I have been testing this across 2 tenants ( installing the app on both, and using users/attendees from both ).
One is our pay-for corporate tenant, the other is a long held (90 day) development tenant.
Both have very much Vanilla policies in place (generally default / managed by Microsoft).
When I test with a small group of attendees (one corporate, three dev) with an meeting booked on either tenant it seems to work well (using a mix of browser and android).
When I test with a larger group of staff (mix of browser and all platform's clients) it seems to fail for almost everyone (including users it worked for in the smaller test)

Steps to setup :

• create app registration, multi-tenant and type of account then update in manifest (id)
• publish a simple hello world html file and update manifest (contentUrl, websiteUrl, validDomains)
• create and publish manifest.zip ( admin.teams.microsoft.com -> Teams apps -> Manage Apps -> Actions -> Upload new app )

Steps to recreate :

• book a meeting inviting some attendees
• start meeting and wait for some attendees to join
• click on to apps (top ribbon in meeting scope) search for and add your app

Expected behaviour : Tab button is added for all attendees
Actual behaviour : Tab button appears for a small number of attendees ( seemingly the greater the number of attendees, the higher the failure rate )

I have attached an example manifest (FWIW).

manifest.json

[microsoft-github-policy-service]

Hi @pugelarouge! Thank you for bringing this issue to our attention. We will investigate and if we require further information we will reach out in one business day. Please use this link to escalate if you don't get replies.

Best regards, Teams Platform

[Prasad-MSFT]

Thanks for raising your issue. We will check this at our end and will update you accordingly.

[Prasad-MSFT]

Update:
We have raised a bug for this issue. We will inform you once we get any further update from engineering team. Thanks!