The send box disappears when the message scrolls down.  The message needs to be really short to keep the button there 

I had to copy/paste a message and send it to fb to go on pc to send it instead. 

Edit: same as Con - I have an Android phone (Samsung S10)

I have this issues as well. I am using an android phone.

Tifi, I know this isn't a "fix" per say, but I installed firefox on my phone and it completely solved this issue and the entire site runs better on the firefox app. Perhaps give it a try, if you are able.

I use my phone for HP and this happens as well if you hold your phone upright(hotdog style), but if you rotate it(hamburger style), the buttons will show back up!

Oooh useful to know Aza. Will try that. Random message to someone on it's way xD

We are hoping to swap the layout to a more mobile responsive one in the near future! But in the meantime, can you maybe send me a screenshot? That way I can see how it's different on your phone than mine.

I can send you a screenshot tomorrow Sam however the workaround of putting phone to landscape works.

Okay :). No rush!