can't watch apple tv on browser

If you can watch Apple TV+ on iPhone, then you should also be able to watch Apple TV+ in a browser on a (reasonably modern) computer (or smart phone, or tablet). Apple recommends Firefox or Chrome for computers (or mobile) without the Apple TV app.

Browsers on smart TVs are often lacking in support for some advanced web technology as used for the site, and may not work.

Watch Apple TV+ in a web browser - Apple Support

The web access is for Apple TV+ content (Apple Originals). Other Apple TV app services are not supported on the web.

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If you had an Apple TV+ subscription before trying out Apple One, then realize that Apple One starts out with a one month trial for services that you haven’t tried before, meaning that Apple TV+ would not be included in the first month for previous subscribers. Users would need a one month overlap for a seamless transition. After that, the redundant subscription would be canceled automatically. If such applies to your situation, then you may want to re-subscribe to Apple TV+ for a short while, or else wait out the first month.

did you click the login in button in the upper right corner?

if you don't wish to see it in a browser then in the usa app store there is the beta version of the appletv app for windows 11 Get Apple TV - Microsoft Store