Why cant i add plugins with add-ons and cant i make changes to the script of plugins like discordSRV?

[Garsy_YT]

So i have a minehut server and a discord server for it but when i look at a tutorial and follow him when i get to the files of discordSRV it says: "An error has occured, Please try again later!" But the same happens when i go to the add-ons i get the same message. But i have had this thing for like 5 months now, can anyone help me PLEASE

 

[DuckyProgrammer]

Download plugins from SpigotMC - High Performance Minecraft and upload them to File Manager -> Plugins.