Help Host in other country can't see me on wifi

[meeeee]

I am taking classes with a teacher in Vietnam over zoom. (Im in USA)The problem is he can't see or hear me when I use my laptop connected to Wi-Fi, he has no problem when I used my phone seeing or hearing me. I could see him and hear him fine on my desktop. 

I had my brother create a meeting over 5G and I joined his meeting from my desktop, he could see and hear me just fine.

Has anyone had issues with people in other countries not being able see or hear them when connected via wifi?

I'm seriously confused and a bit mad by all the efforts I've made to try and get my desktop to work the past few days. The first class he stuck around till I switched to my phone. My class today he cancelled and refunded after 13 minutes of technical difficulties.