I have not been able to get hold of anyone from setupbuilder support but here is what I have found out.
You have to put in your password the first time you sign a file after you log into your computer. It does not work from setupbuilder so you have to do it elsewhere.
The script you are using with signtool works ok for it.
So what I did was make a .bat file to use signtool to sign a single file and it will popup a message to enter the password.
After you enter it for the first time setupbuilder will work fine until you log out of your computer.
I called Sectigo and they confirmed I would need do it this way.
Hopefully someone from setupbuilder will fix this.

Greg