I just got another laptop and have installed Winlink Express, VARA HF (4.6.3) and VARAC (50.2). I entered my VARA HF license key and saw the message that said it was registered.
Winlink Express uses VARA HF and it operates at full speed.
When I use VARAC and hit the Tune button, it complains that a registration key for VARA is required.
I had entered my callsign and the special suffix "QRP". Seems VARA HF didn't like that. I changed my callsign in VARAC and deleted the QRP, saved the settings and exited. I deleted the callsign and registration key from VARA HF and quit VARA HF.
I restarted VARAC and when VARA HF opened, re-entered my registration key. The Tune button worked normally.
It seems that when first installing VARAC, do not use the special callsign suffix until AFTER you've fully set up VARA HF and entered the registration code for VARA HF.