Okay, first, don't mean to be insulting but did you check in the lower-right-hand corner of the desktop to make sure it's 10122? Just had to check since you're only the second person here able to install.
Second, if it really is 10122, how did you install? Is yours Win8.1 > previous build > 10122, or Win10 clean install > 10122? Just want to see if there's anything in your configuration that made it work for you and not for us.
Remember too this is on a desktop machine. Don't know if people are having more trouble with SP's than desktops or vice versa.