Validating a signature fails

[prillerc6507246]

When we are validating a signature we get the following message: Signature validity is unknown.

We use  an Adobe Acrobat Reader DC Version 2019.008.20074.

1.) What URL should I insert under "Load security settings from a Server"?

2.) What are possible possible solutions?

[kglad]

[moved from Installing, Updating, & Subscribing to Acrobat to Acrobat Reader]