Party Video/Audio only works if we start a new campaign every time

I bought Lost Mine of Phandelver and ran our first campaign with 3 others with successful video/audio. 2 have come back tonight to test, but none of them can see or hear each other. I started a new campaign, and it worked immediately, but we now how none of the character sheets from the previous setup that took 3 hours to build, and we're wondering if this is going to fail again. I read the same bug existed 4 years ago... Is there a fix.

The AV of Roll20 is quirky at best. There is usually a greater incidence of issues as the number of connections increases. I doubt the solution you experienced had anything to do with starting a new game, but was likely just happenstance. Many users opt to use a third party service such as Skype or Discord if they cannot get the connection to behave reliably.

That's problematic being a party game. Our fix was based on someone doing the same thing 4 years ago. Surely someone knows why it doesn't work properly...