If you mean in the phone settings, I don have a Samung mobile so there is not Samsung Account available in the phone settings. I have had it working by logging in via the wearable app. The information in the wearable app about the watch, still shows my Samsung account. I don't know if it does that if I realy would be logged out?
The white page shows up when I go to Galaxy Apps and try to download. After pressing OK at the login question only the white page turns up (as an overlay window) where it stops.