Sound drops out after joining a meeting - ipad issue

we have 3 ipads in the family, but on one of them the sound cuts out after joining a meeting. I've reinstalled zoom, restarted the ipad, created a new zoom account specific to just that ipad, but nothing work. The other two ipads are fine when joining the same recurring meeting. So it sounds like an ipad issue but i can't find any settings that are different to the ipads that work. Any ideas what might be the problem nd how to fix it?