It appears the Linux Server is broken right now. The latest version of the Linux Server appears to be V517.7 but the Windows server and the client both report V518.7 and the client refuses to connect to the linux server even though it reports it is up and running and listening for connections. I confirmed by manually checking Steam Depot and verifying I really am on the latest release for linux.
Just as a test I installed a single windows server and was able to spin up an instance that I can connect to using v518.7, however, I need the linux version to get updated to get my real map running again. Any idea when the linux server will get the updates?