[CURRENT BUG] Failing to (re-)add MeisterTask in Microsoft Teams

Hy All! Using a basic account for trying MeisterTask in action, our project team had already integrated it in our MS Teams-team. As I did leave all group members the option to add/delete apps/tabs, one managed to delete the tab by accident for all. Now we fail to re-add the tab, getting only a saving sign (blue circle) and after some while the notion "We couldn´t save your tab settings. Please try again." (see screenshot). There were no changes made by our admin in the meantime. The fixes we tried so far where:

• the step-by-step from the support site for Teams integration https://support.meistertask.com/hc/en-us/articles/360015778680-Microsoft-Teams
• different members with different access rights trying to add tab
• member with MeisterTask-business account trying to add tab
• members with different OS (Microsoft, Android) trying to add tab
• deleting cache
• disabling firewalls before trying to add tab
• adding the tab in the Web-MS Teams instead of desktop app

We can still all access MeisterTask via the browser, some also downloaded the desktop app. But integration into MS Teams would be essential for effectivity. Now we are basically out of ideas, but before trashing our progress and going back to Microsoft´s Planner/To Do/Tasks, I thought maybe someone here has experienced something similar and could give me a hint? Any help would be much appreciated!