I purchased multiple DLC during the 4th of July sale on Steam and they are not activating in-game. This includes the free DLC content as well as Harmonic and Supremacy. They are showing as checked in Steam but in-game I am not able to activate them and I only get a button that redirects me to the store page in Steam. I have restarted both Steam and my computer as well as cleared the Steam cache. Please help.

Did you recheck ingame? From what I remember, you can check/uncheck the DLCs and additional content in main menu ("Content"?).

I'm running into the same problem, no there's no option in Content as a tag on button. I do remember it use to be but I'm not sure what they wrecked in the new update that there's no option to enable/disable the dlc.