u/karatedungeon

I just got a notification that I no longer have a fico score after not having any credit history for the last 6 months. I've only ever had 1 credit card that I kept for several years and paid off and closed (I didn't know this was a bad thing) and a car loan that has been fully paid off as well. Both accounts were in good standing when active and I never missed any payments or anything. My score was at 740 and now it's reading as un-scorable. Do I just need to open a new credit card? Am I starting back from scratch or will my previous credit history be taken into account? Any help or info would be greatly appreciated