This isn't a solution per se but I had the exact issue you're having on a Z590 system using a copy of Windows downloaded from the MS site and then used Rufus to put it on USB, no internet even though Device showed it installed, legit key too. Installed 5 times, same thing then installed a copy of Windows from "elsewhere", worked like a dream and activated with a proper key. Never did figure it out but I'll never use the MS site again