it reads

"Failed to connect to server

Failed to process config from server: refurbished_furniture:server"

what has to be done with the mod to fix this?

Make sure they are using the same version as the server

MrCrayfish i am also having this problem im on the same version as the server too other people can join fine

My server is having the same issues, but we have the same versions. I am running on MacOS on Prism Launcher if that changes anything.

Can you send your game logs of when the error happened? Use https://mclo.gs/ to do this.