Why are directories not created on the FTP server, and photos are not uploaded to the server when everything worked on the local one?

Question

FTP

I took an FTP server from a friend, transferred my project to it, started testing - an error.

On the local server it works without problems. My point is this: there is a first launch, it is necessary for normal functioning, that is, there is the registration of the first user, who later adds others. When registering, a directory is created on the server where his profile photo (avatar) will be loaded, but not a single script in which directories are created works.

Gives out http error 500.

I created a user through the database, created a directory myself, and decided to install an avatar for him - it doesn't work either (the photo doesn't load)

What's the problem?

I use regular mkdir.

I read that there is ftp mkdir, but it also does not plow, because you need to connect there. I did it - it does not connect.