My chat messages to 'everyone' not visible to the host and some participants during meetings.

Hi,

If I join a meeting using my basic Zoom account and I type a message in the the chat to 'everyone', I can see the message and it shows up on my screen alongside all of the other messages posted by others, but the host can't see it and only some of the other participants can see it, but not all.  I have been on a number of courses on Zoom recently and it looks to the host as if I am not contributing to discussions when I am, so I have to keep  apologising and explaining that the chat function is not working properly for me. I have searched Google and Zoom for why this might be happening with no luck. 

Any help on how I might resolve this would be so welcome - thank you so much.