Not seeing or hearing some participants

For the last few months sometimes when I’m hosting a meeting on my pc, I can’t see new participants who join. But the other participants can see and hear them. So then I’ll log out and log back in and often then I can’t hear anyone. So then I’ll try my laptop and it’s the same thing. Then I’ll go to my phone and that’ll mostly work ok. 
but then today I was hearing on participant for most of the meeting until right at the end and suddenly I couldn’t hear her but everyone else could. 
Is this an issue with my internet, computer settings, zoom or something else?

It makes using it as a host useless if I can’t see or hear the participants. 
Thanks for your help.