The selected form cannot be opened correctly because it was signed with a certificate that is either expired, revoked, not ...

The selected form cannot be opened correctly because it was signed with a certificate that is either expired, revoked, not available on this machine, or is not a code signing certificate.  To remove the certificate and open the form, click OK.Note that removing the certificate might require users to delete and reinstall the form on their computer. In addition, forms requiring full trust will not open correctly unless they are signed with a trusted signature.