I’m using tethering for internet. I’ve struggled with not being able to load maps. Sometimes it would work but for the most part it wouldn’t work at all.
Well today I’ve gotten working perfectly. It seems as though heavy chat usage interrupts map downloads for whatever reason. Just leaving all chat rooms seems to work.
If having to leave chat rooms every time you launch the game is annoying, you can turn off the rejoin/auto-join settings in the Social tab of the options menu.
Edit: Joining any chat room seems to block downloads.
I had to turn off Windows Firewall for the connection type I was using at the time which was private and i had already allowed SC2 through the firewall for public and private network profiles. After i turned off the firewall I loaded the game and went to custom and melee. only one map loaded but it was a new one (before i could only see bookmarked maps and still not enter a lobby when picking a bookmarked map). So let it set there with the one map for awhile and when i came back 15mins later all the maps had loaded and i could get into a lobby. for fun I exited the game, turned the firewall back on and loaded up SC2 again all the maps loaded right away and i could get into a game. I don’t know if this will last or if i will have to turn off the firewall again later, but give it a try. I’m using Windows 10 v1909.