Often1

People have their GE revoked for reasons having nothing to do with violations of the law, certainly non-criminal.

It could be as simple as GUWonder points out, as untoward social media posts, travel to destinations which raise red flags, one-way tickets, who paid for the tickets and then related conduct by someone using the same address.

Going to a GE enrollment office is a mistake because they have absolutely no authority to adjudicate and make changes. It is possible that you might be directed to one if there are identification or other matters which need to be verified. But, if you show up unannounced, the result is likely to be somewhere from entirely neutral to hostile.

At this point, you may want to make a FOIA request. That can take forever and is not likely to reveal anything useful, but it might. Additionally, there are some reports that FOIA requests have resulted in further file review, although you should not count on it nor is that properly part of a FOIA request.

Finally, if your current position does afford you access to various law enforcement databases not accessible by the general public, you should carefully review the law and rules regarding access or having others access on your behalf, before doing so.