Collection Missing

Just updated to 5.2.0 and now my whole collection is missing (saying it can not locate tracks and has “!” In the far left column next to them). I haven’t moved any tracks at all, all in same place on my portable hard drive. I read that if you relocate one track it might update the rest but that didn’t work. Do I have to completely remove my collection (20,000 tracks) & re-analyse them???