This almost always means you are logged into a different account than the one on the team.
Check the email at Settings > Profile. It must match the email your admin invited.
If it is different, log out and log in with the invited email.
If you signed up with Google, make sure you picked the right Google account.
Open Settings > Team. You should see your team name and your name in the list.
Still seeing the paywall? Your admin can check Settings > Team to see whether you are listed or still Awaiting response. If you had a free account before joining, email [email protected] and we will merge it into the team.