Usually one thing: you're logged in with a different email than the one you subscribed with.
Your subscription is tied to the exact email you signed up with. Log in with another one and the app looks locked.
Check which email you're logged in with (profile picture, My Profile).
Check the email on your receipt.
Log out and back in with the email from the receipt.
Still locked? Open the chat and send a screenshot of your receipt. We'll have it fixed within 24 hours and you won't lose any days.