High availability sql server, secondary replicas can't be connected on the Availability group
The AG are using "Database Mirroring" Endpoint to communicate between all nodes.
Your SQL Service account need to have "connect" permission on the endpoint.
You also need to grant "ConnectSQL" to the other node service account (or the Server - AITS\PLSBDATEST2$-  if using local service account).  

So to recap, on PLSBDATEST1, you will have a login for PLSBDATEST2$ and you will grant permission to the AG endpoint to it. on PLSBDATEST2, you will have a login for PLSBDATEST1$ with same permission.  

That should do the job.