I was having this too using the dhcp on my draytek router and testing tftp from another machine reckoned it wasn’t responding but did locally. I have up and reinstalled with ftp as dhcp And took off main network it sure if dhcp setup opens ports or doesn’t something else? Even with firewall disabled mine still times out

Well found out what was killing VMPlayer from Network booting it was Symantec Network threat protection causing the issue when disabled it works just the way it should. Now I just need to find where to add an exception for vmplayer so I don’t need to keep disabling the network protection.