Application keys are used only by Legacy MPVI devices, not MPVI2 devices.
MPVI2+ uses a Verification Code, which can only be obtained through the software once the device has connected. This verification code is required in order to complete the registration process and for your device to show up under your account.
Here is what it says on the website:
I have done this.
In the VCM Scanner itself, it says this when you click "Resync Interface".
View attachment 362531
Same thing in both VCM Scanner and VCM Editor. As you can see - it is sync'd and updated.
But I still get this:
View attachment 362532
Obviously, I think I've gone as far as I can go with registering/updating. I have contacted HP Tuners to see if there is some path forward to claim my two pre-purchased credits.
BTW, the receipt I got with the device, does show 2 purchased credits. Also, in the instructions, a note at the end of the process says:
So I would guess this has happened before.