Why is the service asking me to register for free trial when I already have an account?

When you are signed in with your Apple ID account to which the Apple TV+ subscription is linked,

then you shouldn’t be prompted for a free trial or other signup anymore.

It seems that something is preventing proper functionality.

Do you use the web access or the Apple TV app for Windows?

For web access, Apple advises to use Chrome or Firefox.

For web access, try clearing website data (cookies) in the browser (for the apple.com domain).

How to watch Apple TV+ and more - Apple Support

For faster back-and-forth than a forum, you may consider contacting the Apple Support staff for assistance.

I'm in Australia and having this same issue. Can't watch anything on https://tv.apple.com/au browser. But if you click on the open in Apple TV+ (if you have an Apple device), you'll be able to watch on there.

Not my preferred option as Apple TV doesn't automatically go to the next episode etc.

There must be some issue with viewing on browsers - was working fine for me last night.

Same here Australia. Support via the chat have no clue but definitely not working in any browser. Was fine up till yesterday though.

Seems it's not just me then

New Zealand here, same issue. cleared cookies, tried over and over again to re-log, going on 24 hours and still have all the free trial buttons.

Working again now!

I can no longer watch anything via the app either now.

Get the same trial screen as browser.