Serial is still an option for editing the player's config file.

Note: If your player is already configured for dynamic IP addressing, and your computer is configured for dynamic IP addressing, then editing the player won't do any good, you've got a different problem there where either the player or the computer is not talking to the DHCP server.

What were the IP addresses of the computer and the player?

If one of them was 169.254.x.x, then that's the issue, one of them isn't talking to its DHCP server. There's a networking problem unrelated to the player configuration, you need to solve that networking problem first.