@nicolas-moraes I managed to solve it and in my case it was not a FOG or network issue. I verified that DHCP was working correctly (confirmed with tcpdump), options 66/67 were unchanged, TFTP was running, and the FOG web/ipxe boot.php were reachable.
The key test was that when the client stayed at “Start PXE over IPv4”, the FOG server was not receiving any DHCP or TFTP requests at all, which pointed to a client-side problem. Even though Secure Boot and Fast Boot were already disabled, the issue was caused by the BIOS state.
After restoring BIOS defaults on the HP laptop and re-enabling PXE IPv4 boot, everything started working again. It seems some UEFI/PXE flags were stuck, and resetting the BIOS fixed it.