not able to add "i:0i.t|00000003-0000-0ff1-ce00-000000000000|app@sharepoint" as contributor

Hi All,

i am not able to add appidentifier "i:0i.t|00000003-0000-0ff1-ce00-000000000000|app@sharepoint" as contributor to TermStore Group in SharePoint Online. The appidentifier is not resolving and not allowing to add.

Few weeks back  i was able to add in classic mode, is Microsoft disabled now?

Also there is no way to switch back to classic experience/mode.

Any one having any solution or fix for this issue?