I am using SketchUp Go on my iPad. When I try to create a new file it tells me to Upgrade
However I am subscribed until June 2023
That means you are either not logged in, or logged in with an account that is different from the one you used to purchase your subscription (99% of these posts are usually because someone is logging in with an email that is different from the one they used to subscribe).
If I were you I would log out and log in a gain making sure you are using the correct credentials.
SketchUp go? Or SketchUp for iPad? Because my iPad log in screen doesn’t look like that.