Hi everyone! So someone replied to me on reddit with a fix! I don't know how permanent it is but it worked for me!
Simply open your terminal (for Mac users press Cmd+Space and type "terminal") then paste the following code:
chmod +x /Applications/Twitch.app/Contents/MacOS/TwitchAgent.app/Contents/MacOS/TwitchAgent
Then relaunch your Twitch and the Mods tab should show up (I had to refresh once for it to work).
Hope this works for you too!