So I finally have a chance to be landside in FRA, and I have an exceedingly dumb question... where is the enrollment center? I looked around for maybe 20 minutes tonight before giving up. I found a Bundespolizei office next to the security checkpoint into Z from T1 Hall A (level 3), but it seemed to be closed (was ~19.30). Hours online claimed until 21.30 but "core hours" were only until 18.00.

Reading the comment thread makes it seem like that was wrong, but I didn't find anything else likely-looking, hmm..