The redirect URL you provided for your registered app under https://www.twitch.tv/settings/connections does not match with what you provided as a callback. They have to be 100% identical.
What is rails passing in as the redirect_uri to Twitch when it calls the API? Maybe that is getting corrupted or is not what you think it is? Assuming you are still having the redirect error.
Are you sure that when you hit save, chrome/browser didn’t accidentally wack a / on the end as a auto complete measure. I’ve had that happen and it’s caught me out once of twice.
But recheck ALL your settings, to make sure you got all the right keys/clientID etc
A Google for “OAuth-Twitch gem” returns Three results with the same name but different authors. Which are you using?
Oddly, that didn’t seem to change anything. I then altered the route slightly and it worked perfectly. I was then able to alter the route BACK to what it was, and it still works.
I think I may not have restarted my server in between those steps, and I’m assuming that specifying the gem was the key here. (I was trying to be diligent about restarting the server whenever I made a change, but I can’t be positive I did right after that step).