ENI got detached from FSx

I have an FSx for Windows file server which was working fine for more than an year. Somehow the ENI got detached from the FSx automatically and the file system went to misconfigured state suddenly.

Please let me know if there is a way to reattach it or get the FSx back to working state. I tried to create new FSx from Backup but it always fails with the error insufficient permissions or connectivity to Active Directory. Though we use the Service Account with necessary permission and the connectivity to AD is fne.