Session Mgr: 500 Service Unavailable

[svasud]

Config:

CM - 5.2.1
ASM - 6.2
Endpoints - Avaya One X Communicator

Trying to make test calls between two SIP stations registered to Session Manager and seeing "Rejected - 500 Service Unavailable" error in the traceASM logs.

Also, tried to trace on CM, when I make a call from one station, though the trace starts on that station, I see no activity on the called station plus I get a fast busy. So, there must be a disconnect in between but I am not able to figure out where the place of disconnect.

While tracing calling station on CM, I do see these denial events:

17:37:10 denial event 3731: Incompatible caps for end D1=0x7f400006 D2=0x500
06
17:37:10 denial event 2300: Ept capabilities mismatch D1=0x2 D2=0x2
17:37:10 denial event 3731: Incompatible caps for end D1=0x7f400006 D2=0x500
06
17:37:10 denial event 2300: Ept capabilities mismatch D1=0x2 D2=0x2

Can you share your thoughts if you had similar issues in the past or if you know the solution to this issue?

Thanks in advance!