It may be for the following reason:
and check the following posts about how the other users solved the similar issue -
Market Tab Error, show a blank page and missing optionhttps://www.mql5.com/en/forum/170760#comment_4177231 andhttps://www.mql5.com/en/forum/71467/page2#comment_9026436
Are you using Mac?
MT4 for Mac do not have Market tab
It is not related to MacOS ... because the latest MT4/MT5 builds are dealing with MacOS concerning the Market in normal way.
He needs to check about what I told him on my previous post ( to check step by step, and if not - just report here on this thread).