Avamar Proxy Deployment Manager handshake_failure

Has anyone seen this, and/or know how to rectify it?

Avamar 7.5.0, vCenter 6.7

I open the Proxy Deployment Manager, then hit "Create Recommendation". I then get a subitem under "Loading recommended proxies..." that says "Received fatal alert: handshake_failure"

This is an existing deployment that just needs some cleanup. Most backups work, and it can log into vCenter just fine...

Some log investigation also indicated that the Proxy Deployment Manager may be its own app, or at least uses its own port, 8543. Pulling that up in a browser throws all sorts of interesting "secure connection failed" or unsupported TLS version errors. So, I tried to have a look at the cert to see if its expired or something by running openssl directly on the node:

admin@myavamar:~/>: openssl s_client -connect localhost:8543

CONNECTED(00000003)

216161:error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol:s23_clnt.c:610: admin@ncavamar:~/>:

This is a single-node Avamar with a Data Domain.

Anyone know what may be causing this? Something appears to be up with the port 8543 service. But I don't know much about Avamar, having just inherited this one, and I don't really know where to start digging...

Many thanks in advance!