Does anyone faced Attach Reject with cause No suitable cell in Tracking Area?
Yes,it could have different reasons.
Issue in Core?
It was working fine in the past.
Authentication issue, IMEI issue or ban TAC for specific PLMN. And could have this cause according to MME configuration.
Whether observed for a particular UE?
No, all UEs
Most of the time it’s bcos TAC is prohibited in MME.
We recently faced this issue when by mistake a core guy blacklisted a TAC in MME.