i just made a new twitch account on my phone and successfully linked it to my xbox but when...

Hi Cf9_db. My name is Kyle and I'm an independent advisor.

Try power cycling your Xbox to see if it refreshes the linked account:

Turn off your console by holding the Xbox button on the front of the console for approximately 10 seconds. The console will turn off.

Turn your console back on by pressing the Xbox button on the console or on your controller.

Thanks for trying that. Have you tried unlinking and relinking your new Twitch account?

I am having the exact same issue but on the Xbox series S. Twitch says I've successfully linked the account but Xbox button just spins.

Just go to twitch activate and link your xbox one twitch account from your phone and it will add your twitch account on to your xbox one twitch app. I've just done it myself. It will ask you for the code from your twitch account from your xbox then pop it
in and it will link which account you wish it to.

Confirmed this issue as well. When trying to link my account on Xbox console and thru Xbox PC/app, when I enter in the code to verify twitch, it spins and never finishes.

After reading this forum, I tried connecting through the Xbox app on iphone, and it auto-connected to my twitch account.

Currently connecting via your phone app seems to be the only way. Hopefully Microsoft fixes this soon.