Same issue here. Tried starting with default settings on Navezgane, and also tried again with "run server update" option selected; will not start. Thinking about requesting a refund, as this seems to be a common issue and makes the setup far from the "instant" that's advertised on the website.
I had no problems with the Valheim server I hosted, but the 7d2d hosting service here seems to be less of a priority.