I currently own PICO-8, but the website doesn't think it needs to be updated. Anybody know how to fix this?

Even if you already have the current version, this site would still show you a download link for it if it knew you owned it.

Which site did you purchase PICO-8 from?

• humblebundle.com
• itch.io
• lexaloffle.com

If you bought it from humble, do what it says to do in your screenshot:

This is the link from the screenshot:
https://www.lexaloffle.com/account.php?page=activate

If you bought it from itch, then you need to download it from your itch account:
https://itch.io/my-purchases

If you bought it from lexaloffle, then you have to log in to the account you bought it with, and download it from the page you already know about:
https://www.lexaloffle.com/games.php?page=updates

Got it on lexaloffle, it's still not working