ran into the same problem; disabled my mods, restarted the game and the channel appeared. Sent my sim to sleep, completed the quest, then re-enabled my mods and restarted my game.
i used Sims 4 Mod manager and deactivated all my MODS and CC and went through all of them! Cleaned out my closet so to say things i didn't use and reactivated bit by bit going in and out of my game. I also noticed some players have the problem 'cause they didn't redeem/claim the event item. I also got rid of most of my CC electronics; like radios, tv's and tablets. Honestly after 11 days of cleaning out and going in and out it started working again, i cannot tell you what really was the issue
