Have you gone to "members" -> "search members" and entered his username there? If not, try it. If you have and nothing comes up, then you must not have the right username...
Can't find friend....

I am searching for my friend he's just joined up putting in his username but search comes back negative he also has tried to search for me, any ideas?, Thanks
Whats the persons username and i'll check for you?

It's possible the databse that handles the search for members is not updated yet if he just joined. Is he able to log in? If so, he can go to his profile page and send you a link to it.
I could not find my friend nor myself on the mobile app. I had to login to chess.com in a browser, then go to Social, then go to Members. I can find myself and my friend no problem in the browser app. I'm not sure if there is a setting to allow for me to be searched in the mobile app or perhaps I need the premium membership which I do not have.
My friend received my request and accepted the request. Now I can see my friend under friends in the mobile app.

We believe some things like clubs and socials are restricted when you are on the app. You only gain full functionality of the site on desktop.
I am searching for my friend he's just joined up putting in his username but search comes back negative he also has tried to search for me, any ideas?, Thanks