ERROR 38031

If you have a known good SMB & known good resolver, then the issue is the cable.

Does this happen when before motor power is on or when you try to move the robot?

Shielding issues can be hard to find. Make sure the cable shielding at the SMB is tied to ground with cable ties.

I worry when you say you changed the resolver - removing the resolver from the motor will effect the motor commutation values.

Can you verify the SMB is good?

I've also seen this happen with a customer having various model S4C IRB2400 where the wrong wire harness was installed and while the wires checked good, the connections were incorrect.