I'm living in the UK but had exactly the same problem. I found some advice that changing DNS on the TV to Google (126.96.36.199 or 188.8.131.52) would fix issue with connection and it actually did.
I don't think it really matters but I've pihole setup at home and once I set DNS back to auto, my TV is losing Internet connection.
So with a combination of logging into account.samsung.com with a browser and removing my tv device from my account, and then changing DNS from my local pi.hole to google DNS on the TV settings has allowed me to log into my account on the tv.
I had the same problem. Soft resetting the TV solved it! Press and hold the power button on the remote control for more than 3 seconds and wait until this reboots the TV. Then try it again. Hope this helps others! I did not lose any of the other installed apps...
I tried the power unplug, and resetting the network connection solutions but they didn't work. Doing a factory reset fixed it for me. Just know that you will have to reconfigure everything.