I have several users who report that they are unable to sign more than one document at a time. We are using Smart Cards that hold the certificate and when we try a 2nd time to sign a document the field where we enter the PIN is missing. At this point we must close Adobe DC and restart.
Could you please let me know the version of Acrobat DC installed on the machine?
To check the version of Acrobat, launch Acrobat>navigate to Help menu>select About Adobe Acrobat...
Which Operating System is installed on the machine- Windows/Mac?
Adobe DC 2015 release
I'm running it on a Mac with MAC OS 10.11.6