I tested a new device using HLK Studio and added the driver package to the resulting .hlkx file. I successfully signed the file as well with our EV certificate.
However, parnter center does not accept the file and no info about the error is given:
You might want to check your account access settings on the Microsoft Partner Center and verify that your account has been given Driver Signing permissions.
On the Partner Center website, click the gear in the upper right corner and choose "Account Settings". Then click My Access. You'll see a Hardware section in the middle - make sure it says Access Granted.
@Ernie_Coskrey Hardware access is granted. I actually send a few .cab files previously to sign and it was successfully signed. Now, I can't sign my driver , which uses the binary file of another company's signed driver, using .cab file. Thus, i wanted to try to sign it with HLK.
@rob18767 I didn't receive any email like the example you gave.
I just reset the Client machine to its manufacturer settings and installed everything again. I can upload the .hlkx file now. I don't know what caused the issue, but installing the client on a clean system solved it.