Tenant still getting the old Exchange admin center message trace interface

Hi FM-CVTG, if only one tenant is still landing on the old message trace interface and traces are failing, that is probably not something you can fully fix from the tenant UI. I would first test message trace from PowerShell using the Exchange Online module to confirm whether the backend trace service works. If PowerShell works but EAC does not, gather screenshots, tenant ID, browser HAR if allowed, and the failing trace details, then open a Microsoft 365 support case. Also test with a Global Admin in an InPrivate session to rule out cached portal state.