There are a couple of things you can try to correct the issue.
1. Go to Settings>Applications>(Select More Options and Show System Apps)>Find the Bio-metrics app. When you open it, select Force Stop. Then select Storage and Clear Cache.
2. Place the phone in Safe Mode and see if you are able to set up the fingerprints. https://www.samsung.com/us/support/answer/ANS00062983/
Let me know if this resolves the issue.