Setting up a new workspace or conversation thread for collaboration in Microsoft Teams
Dear BeVer_NL,
The issue was confirmed to be related to a bug, and it will be resolved soon.
The work around we used to get past this issue was to navigate add the users with bulk operation from Microsoft Entra.
Visit entra.microsoft.com>>Groups>>Select the group of the Team that you want to add users to>>users>>Bulk operation>>Import member>>Download a Csv template (CSV1)
Navigate to the group that contains the users you want to add and download the users to CSV2 of the group using the same step above.
If Csv2 is not arranged, click on the column A>>Click on Data in excel>>Text to column.
Preserve the prefilled cells in CSV1
Copy the object ID of each user from Csv2 to each row of CSV1. Save settings and close CSV1.
Navigate back to the group that you want to add the users to>>Import members>>Upload the updated CSV1 and submit.
This will add all the users in in the excel sheet to the affected group and then get synchronized to the Team.
Thank you.