Hi Bernd...
>>>has something changed?
Lots of things have changed. With commodoca and other signing/stamping
authorities.

From what you've said the problem is probably not the commodoca signing URL
at all, but your certificate.

Take a close look at your certificate using CERTMGR.EXE or MMC.EXE.
These are both Microsoft utilities available for the Window 10 environment.

Does your certificate have an expiry date more than 12 months out from the
sign date?

What are the certificate's "Key Usage" settings?
Anything other than Code Signing (1.3.6.1.5.5.7.3.3) may be too broad
purpose and no longer admissible.

Most important of all:
What is the certificates "signature algorithm"?
All variations of SHA1 (for example SHA120) are no longer admissible.
Code Certs should be signed at a minimum SHA256, preferably SHA512


Cheers...
Gus