I've seen that error a number of times, and if the JAMF binary is intact on the machine, you'll just need to run "sudo jamf enroll -prompt" and enter the username and password of a JSS user. I think you'll also get prompted for entering an SSH user, but you can leave those entries blank. Since it requires you to enter additional information, you can't execute it as an ARD UNIX command, but if you launch Terminal on the machine or SSH into it, you should be able to get it re-enrolled without issue.
Alternatively, you can use an invitation ID that you create in the JSS. On the left-hand sidebar, you can find "Enrollment Invitations", where you create a one-time (or multiple, if you desire) enrollment invite, including an expiration date/time and a default Site in which to enroll the computer. The invitation will be emailed to an address that you provide, and you can grab a long number at the end of the URL (should look like invitation=XXXXXXXXXXXXXXXXX...). From there, you can send out the command "jamf enroll -invitation XXXXXXXXXXXXXXXXX..." as root in ARD to the machine you need to get re-enrolled, and then you don't have to mess around with any entering of credentials.
