Hello Bjorn,
Thank you for your followup on this and for sharing the details with us - I am sure these will be of help for further users facing a similar scenario.
We are working with Digicert to resolve this. I'm curious whether this is caused by Advanced Installer calling signing of each executable and dll separately instead of in a single call. which can amount to a lot of signings in a single project/installer build.
This might indeed be a possible cause for this issue. However, this is quite interesting as I wasn't aware of any limitations when it comes to the number of files you can sign. Please keep us posted with more details from the DigiCert teams.
If that is indeed the reason, I might be able to present this to our dev team to see whether we can make an improvement regarding this - I am thinking that perhaps we have gone this way because signtool does not allow signing multiple files at once (or does it? I will have to further investigate this as well).
Best regards,
Catalin