Go to setting --> apps--> Samsung Pass (click on the 3 dots on the right hand corner) --> uninstall updates. This will reset Samsung Pass, which erase all of saved passwords but will definitely fix the issue.
I had the same problem.. What worked was:
Delete the Samsung pass entry that stopped asking for your finger prints.
Close out all you applications
Go to the wesite (it should appear as though you've never been there before)
Enter your credentials (user name and pasword)
Samsung pass should: ask you if you want to remember the site, tap yes.
Close the website and internet app.
go back to the site and see if you are asked for your finger print, if so: you've successfully soleved that prblem. If not, contact samsung support.
I disabled my Wifi connection so only cellular data was used, and then it worked. I have seen that with several apps that they only seem to work over the cellular service or Wi-Fi service (particularly for Smart home devices). Try that and see if it works.