I get the same thing. I use my 10 digit personal ID number that is on the first page after I log in using "apply", along with my regular login info, but track says "you have not applied to UCAS".
I haven't got my welcome letter as of yet, but then again is the number in that letter really going to be different than the personal number on the first page of apply when you log in? From everything I've read, they're the same.