load balancing failed to find a valid mailbox database exchange 2013

single exchange 2013 server CAS + MBX.

single database.

When create new mailbox it have error load balancing failed to find a valid mailbox database. we need select the Mailbox database manually.

Checked mailboxdatabase -IsExcludedFromProvisioning and -IsSuspendedFromProvisioning $false

Any idea?

Thanks.