I believe the fingerprint process is same for green card and TPS, so I will weigh in here. Yup, its normal to be rejected by FBI for fingerprint. USCIS let you try three times(for green card and I hope its the same for TPS), and if FBI rejects all these three, then USCIS will ask you to provide police clearance report from all states and countries you have lived after you turned eighteen. My friend's fingerprint was rejected three times for GC and she had to provide police clearance letters to USCIS.

I read somewhere that you can buy some lotion/gel , which helps to improve your fingerprint screen quality. http://ask.metafilter.com/130462/Any-tips-on-how-to-become-more-fingerprintable