Members can comment but cant see comments from others

I am using a desktop all works fine. Most of my members use a phone either Samsung or IPhone. A lot of them are finding they cannot see chat comments. They can comment they can access the chat box but they can not see other members comments. Can someone tell me how to rectify this.

Could it be that they can not see the message area because the screen of the phones is very small? Or do they see the message area and it remains empty?

they can see the message area. They can comment, but they cannot see any replies

Can you have one of them take a screenshot? That would be very helpfull!