"A network or server error occured" after Hub Factory reset

I am preparing to sell the house and did a factory reset on the Smartthings Hub (STH-ETH250). When trying to set it up under the new account, I get an error message “A network or server error occurred. Try again later”.
Same happens when I try to re-connect to the old account.
Cache and data have been removed from the phone (Android). App is the latest:
Does anybody have an idea what I did wrong?

I’d try logging into the IDE at https://account.smartthings.com to see if the Hub might still be attached to the account but in an “Inactive” state. Click on “My Hubs” to view all Hubs currently associated to your Samsung Account. Clear it out from there and try resetting it again for good measure.

Hope this helps.

Thank you Garrett. The hub is not attached any more to the old account: “You don’t have any hubs yet. Please use the SmartThings mobile app to claim your hub.”
I think I did reset at least twice. I can do it again but I am afraid that may not do it.

For reset I did:
Power disconnect, battery removal, network cable disconnect
Press reset button for 30 s until blue light blinks while powering up
Plug in network cable after about 15 min
Try to connect to account

Did I miss anything?

This is mostly correct except the Hub’s LED should flash yellow → become solid yellow while resetting. If you want to post or PM the Hub’s SN I can check the status for you as well.

Garrett, it went to solid yellow and then went to blinking blue. After a while it turns solid green
How do I PM you?