No hostile mob spawn in nether

Hello there is no hostile mob that spawn on my server on the nether side but on the overwolrd side all is well my server is a spigot server 1.16.1

Hello yes I can spawn zombified pigiln with egg but before we have a vanilla server and they are this hostile mob but after past this server in spigot 1.16.1 we don't have hostile mob. Can I upgrade my spigot 1.16.1 server to vanilla 1.16.1?

Hey I put my serveur in vanila serveur and it's done thx