Here is the process I made:
Uninstalled Bnet + deleting rest of folders C:\ProgramData\Battle.net and then restarted PC.
After that installed Bnet client again, logged in, checked D2R - only BUY button. Checked also on web side and there’s the same, only BUY button.
Downloaded D2R-Setup from web side account and tried to install it with logging in, sent this message:
https://us.battle.net/support/en/article/32512
I am running out of ideas what else shall I do.
info:
Day later (30.9.) after purchasing the code and error appearing, I created also a ticket in a section Account, App, & Shop, unfortunately with no response yet, that’s why made a new topic here, due to hunger of playing D2 