Unable to validate signatures

Dear,

I'm unable to validate signatures in Adobe for all users logging onto an image. I have already uninstalled adobe and deleted the programdata folder and reinstalled the most recent version of adobe (2021.001.20145)

When I open any signed document, there is shown that the document is signed by unknown. I'm unable to open the certificate details as this link is unresponsive.

When checking Preferences > Signatures > Identities & Trusted Certificates I receive the following error:

"

File or folder does not exist.

File

"

Often it also happens when opening a signed document, when adobe tries to validate the license the following error is shown and the application closes:

"

Invalid Plugin Detected. Adobe Acrobat Reader DC will quit.

"