Not saying it's for certain that this "is" the problem.
But something that can happen quite often is the preset creator exporting their preset with the wrong capital letters or capitals where there should be none. To explain this further I will use myself and my username as an example.
My username is "redlinelies", this is what the server sees it as and even though I can log in as "Redlinelies" with a capital "R", what the game sees me as, and friends and users sees me as is still "redlinelies". If I'd export my preset after/while being logged in with capital R, only I would see this preset and no one else. In order to fix this the user at hand must export the preset and with the correct capitals or small letters as other users see them, otherwise it will not work. In some cases this can cause issues for people so check with your friend in-game how THEY see their username, and compare with how you see it, they'd want to export their preset the way you see their username.
If not that, and it's only you out of a group of users that cannot see the preset, it's more than likely that you didn't install their preset properly because everyone else would get the same preset as you. Do make sure that you place the exported preset that is your friends in the correct folder of the game.
I also want to remind that if your friend has a lot of odd symbols in their name instead of a more plain one with just letters, it could cause issues for users to see them properly. Try to stick only to a-z usernames to be on the safe side.
