They might not have it running either.
In order for the presets to show, their computer must sync with everyone elses and the server that get your preset first, this can take some time depending on how good seeding it is on the preset. Also keep in mind that players MUST restart their game in order to see your preset, you can upload a preset as a user is in game, but they will not see any preset the preset sync has downloaded unless they restart.
-Other user must have preset sync running to ensure all new presets are added to their game(This can take up to a minute before they are downloaded)
-Other user must restart their game
-And like before with old presets, your name matters, if you registered with a username like "Derpball" you must also log in and export it as "Derpball" and not "derpball" lower and higher case letters matter.