When using connecting to a World Partition level on a dedicated server the client get's disconnected immediately. I tested this with a non WP level and the client connected with no issues. I've included logs of the project and of the server
Used this documentation to setup the server on a GitHub build: https://docs.unrealengine.com/4.27/en-US/InteractiveExperiences/Networking/HowTo/DedicatedServers/
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-163742 in the post.