The game doesn't connect to the servers in any way (e.g. online levels dont show up or load and everything in the search, map packs, featured, gauntlets, etc. tabs don't load.) Someone please help.
No matter what you use, probably the most basic possibility is that GD's online stuff tends to break if you've changed your username and/or password recently and haven't gone to the in-game account settings and hit Refresh Login (all you need is your current username and password, no data should be lost). I'd say try that first before you go into the game files and change anything else.
--Jayflight/Jayfrost-- Around GD since 2014, forums since 2017 (even though my account doesn't show it!). If help is needed on a thread, just tag me as "@ exosphere" (without the quotes or space) and I'll respond asap!