Sorry about this posting. I had trouble getting VC knobs working in P3Dv4 with PMDG 737 NGX.
The solution is the same as it was before. (I checked my old messages....)
It has something to do with the FSUIPC.ini file.
I am using the latest release of FSUIPC for P3D v4.
Does anyone know why this is a problem?
The only aircraft I had set up with the FSUIPC was the Beech Bonanza A-36.
Once I deleted the FSUIPC.ini and restarted the P3Dv4 with the PMDG 737 NGX as the first aircraft loaded (Bonanza A-36 is default scenario,) the knobs became operational again.

 

Edited August 27, 20178 yr by AYBABTU
Solved problem but still curious as to why FSUIPC interferes with 737 NGX

Well, it appears that by setting up and calibrating the Bonanza A-36 using FSUIPC, for some strange reason, it interferes with the operation of the PMDG 737 NGX. I edited the FSUIPC.ini by removing all references to the Bonanza A36. It was the only aircraft that I had set up using FSUIPC. I may have to have separate FSUIPC.ini files for each aircraft when using the PMDG 737 NGX.
I have not yet figured out where the conflict is occurring.