Symptoms
Failed Signature Check when downloading scriptcatalog.zip
Cause
The Certificate Revocation List (CRL) is out of date and Protect cannot reach the URL's to verify the certificates
Resolution
Allow the following URL's to be reached
http://gtssl-ocsp.geotrust.com
http://csc3-2010-crl.verisign.com
http://csc3-2010-aia.verisign.com
You can also try the solution in the following document
How to update the Certificate Revocation List (CRL) on a disconnected Protect console server
https://community.shavlik.com/docs/DOC-23601