The same thing happened to me.

It took me a long time to figure it out.

I kept bugging the TSA, and govt office I could find. I just wanted to know.

Turns out, I had a parking ticket in Germany, and didn't pay it. That got me put on a person of suspicoun list..

I managed to find the record and paid the ticket 4 years later -- 70 euros is pricey parking ticket -- but that fixed it.

theres lots of reasons it could happen.