If a Session ended after about 40 minutes, or an invite link worked once and then stopped, the Host is almost always on the free trial.
The trial allows 40 minutes of Sessions in any 24-hour period. The time counts against the Host's account, not the Guests'. When the Host reaches it, the Session ends for everyone, and nobody can join that Host's Studio again until the 24 hours are up. A Guest trying to rejoin may see an "Oops" message.
Let the Host know what happened. There's nothing to fix on your side.
You can wait until the 24 hours are up, or choose Basic or Studio to keep going straight away. Basic and Studio don't have the 40-minute limit. On those plans a Studio closes after 24 hours, long after most Sessions are over, and the Host just invites their Guests again.
See Your free trial and what happens when it ends and Plans and prices.