I have found that if you go into apps. Find Samsung Free and delete cache and app data, then clear this. Open Samsung Free and agree the terms and conditions, mine then worked again.
Glad it has worked. Hopefully permanently. I haven't had a recurrence of the problem so far. Curiously I have a brand new galaxy tab s8 ultra which had this problem after an app update from Galaxy store. So I think there is a bug somewhere in the latest Samsung Free app update.