CLIENT_ONLY WORLD with 1 level issue

Hello! I'm using DH mod for server & client with the same version 2.3.3 but I'm stuck on CLIENT_ONLY world & no communication with server. I've activated both "distant generation", I'm on Minecraft 1.20.1, in the config, server is set on PRE EXISTING CHUNKS ONLY (that's a pregenerated world) & client set to INTERNAL_SERVER. Now I'm completely stuck. Thanks in advance for your help!