so i tried getting this mod https://www.curseforge.com/minecraft/mc-mods/playerex#c51 added in suggestions but was denied because the mod was deemed made only made for client i then checked with the creator to see if the mod was really client side only but he confirmed that it works on servers i even named the server site i used and his reply was this
"Hi there,
I can verify that this mod is both client and server compatible; this is likely an issue with Aternos, and as such you should contact their support about this. Minecraft server hosting sites have the right to not allow specific mods without being required to provide any reason. I recommend using a dedicated server to avoid permission issues.
In future if you have an issue, please raise the issue with the github issue tracker, and provide more information than simply stating the failure mode.
Also, please ensure that you are using the latest version (1.1.7 at this time) as there may be bug fixes that solve issues prevalent in previous releases.
Thanks."
so to summarize how and why is it not working or added 
