When attempting to sign, I’m getting:
SIGNING ERROR:
An error occurred while attempting to load the certificate. Invalid provider type specified.
Warning: code signing failed, an error occurred.
The certificate is a GoDaddy cert. I’ve tried it with both the .pfx and as thumbprint. Same thing.
dcc
Make sure your certificate is for code signing and not just a SSL/TLS certificate for servers.
It is code signing, and it works fine if I use signtool.exe via command prompt.
Is it a EV code signing certificate? For instance, with the private key lying on a dongle?
Nope. Straight up plain old Code Signing from GoDaddy.

Did you try the hotfix we provide?
I wasn’t aware that there was a hotfix! Can you please provide me the link?
Thanks
dcc

Sure, please open a ticket at Support Center - G.D.G. Software and you’ll get it asap.