If you have an IP, try to ping your Distribution Point (DP) or Management Point (MP). :
This error indicates a network communication failure between the client and the Management Point (MP) or Distribution Point (DP) after the machine has initially booted into WinPE
If the client gets an IP address but still cannot download the variables, a network firewall or access control list (ACL) might be blocking the necessary traffic. Ping works, but web requests to the MP fail.
Even if you have an IP address, the driver might be unstable or unable to maintain the connection required to download the variables file.