CityVStars

I am attempting to set up a server on fabric 1.20.4 with both BetterEnd and BetterNether fabric mods. Currently I have added the bclib, betterend and betternether mods, all fabric versions 1.20.4 in the mods folder on minehut, and client side with the fabric api in my mods folder. When attempting to join the server I get Connection Lost, "Internal Exception: io.netty.handler.codec.EncoderException: java.io.IOException: Can't serialize unregistered packet" Does anyone know what I can do to fix this error code? or what it means?