Interestingly enough, my father’s laptop suddenly has this issue and would not display data for both non-season and season achievements.
Just wanted to go through what it took to apparently solve the issue:
This did not fix the issue.
This didn’t directly fix the issue, but not ruling out that cache files weren’t part of the problem. But doing just this step did nothing to solve it.
This I ended up doing a tad different on the first attempt:
I first created a proper direct shortcut to the 64 bit version of the game with the -launcher included. Then I ran that shortcut as Administrator. Logged in and while it wasn’t immediate, within 30 seconds and with me checking periodically, the Season and Non-Season achievement data fixed itself.
I then exited the game and opened it normally from the bnet launcher. Works fine now.
Not sure why, but wanted to update on this particular issue. Thanks.