The recovery server could not be contacted.

I know this has been asked before, but it hasn't been solved, still. I am trying to update to MacOS Mojave from High Sierra. Every time I open the installation application and hit continue, it shows the error message, "The recovery server could not be contacted."

I have tried restarting the computer. I've booted it up on the recovery server and reinstalled MacOS High Sierra. Nothing has worked. I can guarantee I've been connected to a solid WiFi network each time, because I recently updated my MacBook Pro on the same network. Does anybody have any idea how to fix this?