This is moderator from Samsung Members Community.
Please try below steps.
1. Remove your simcard and restart your phone to sign in again.
2. Make sure the software version updated to latest version in Galaxy Store.
3. Uninstall Samsung members app and re-install from Galaxy Store.
If the error continues, try below steps:
1. Log into your Samsung account via a computer.
2. Go to security. Then add secondary security to the account which will be a code.
3. Log in to your Samsung Account on your phone.
4. If your phone locks you out using the password still it will then automatically use secondary security.
5. Samsung will automatically text you a code your phone will sync with this code opening your Samsung account.