When and how often does Acrobat download current CRL files to the security/CRLCache directory?

For Acrobat Reader DC I find, under Appdata/Roaming, a Security/CRLCache directory, with Certificate Revocation List (CRL) files. These are used for verifying certificates for digital signatures, and are provided by an outside authority. How does Acrobat access current CRL files, and how often are they downloaded? I tried deleting the files in the CRLCache directory for Acrobat Reader DC and have been waiting for a few weeks to see if the software would provide a current file download.

Because of this revocation checks are not performed and the signature validity is unknown.

"Revocation checks could not be done possibly because you are not currently connected to a network" in Signature Proberties tab.

"The selected certificate is considered valid because it does not appear in the Certificate Revocation List (CRL) that is contained in the local cache" in the Revocation tab of Certificate Viewer.

CRL processing error

Issuer: cn=xxxxxxxx, xxxxxxxxxx, xxxxxxxxxx

This update: 20170608150530Z

Next update: 20170715150530Z

CRL has expired or is not yet valid____________________________________________________________ In the Problems encountered ​tab..

Please tell what is the issue and how to resolve this.