check why the users subscription were deleted although admin assigned them ative EA subscription

Here's my customer's question about user subscription were deleted in 3rd Apr. due to lifecycle process. but their EA subscription no changed history and assign to users already.

Microsoft service team coudn't help them find the reason . o365 and AAD team all can't reply customer why. they just feedback  Entra ID expired or change . which microsoft support team can help check the audit log or understand the AAD or License assign or any conflit subscription 

Except for EA subscription，we fund they have webdirect trial E5 and Hongkong CSP subscription E3， but customer said the CSP were ended  in 5th Dec.2023, but we fund the current state end date is 3rd Apr. 

Question：1. could it happen CSP give customer 4 month grace period？ how to check it.

2. base on customer words they have already sent the user M365 E5 EA subscription ，why it happened?  I guess if it is CSP  subscription cause the issue , because the users were assigned the E3 from CSP subscription ,although they cancelled renew the CSP , but microsoft gave customer 4 months period , the users still can use the old E3 ,but 3rd Apr. the subscription was deprovioned ,    admin assigned the EA subscription , they must hand adjust the subscription？   how to check if due to conflicts license or product  .