You need to go to Manage Connections (top of the screen that shows your drops), scroll down, and disconnect from OOTP. Then, go to
https://pt26.ootpdevelopments.com/ and log into the account which was previously receiving the drops. Click on Twitch, but don't connect this account to Twitch. Instead, log out, log in with the team you want to receive drops, click Twitch, connect that new account to Twitch, then go back to Twitch and claim your drops there. You can also get to the Twitch connections page from the Twitch link at PT26 if you aren't able to find it at Twitch. Also note that you
must log into the previous account and click Twitch before accessing the new account. Otherwise, it won't work when you try to connect the new account.
edit: I just realized that you changed your Twitch username and not the recipient team. In that case, you probably need to disconnect/reconnect and might then need to follow the above.