@Satender_Pal Hi i do see ou are using Firefox but have you tried using Microsoft Edge or Chrome, secondly is there a Microsoft team desktop client install so you can check on that, besides are all the users in this sub-domain having the same issue or just a few....can you also try creating an account on the main/root domain and check if that works.
even i would suggest checking the account exists on the Microsoft 365 admin center or not and having Microsoft Licesning assign.
