Is this VMware?
Could be this issue: Pxe with uefi katello 3.16
Long story short: GRUB2 in combination with certain firmware has issues in finding ESP, thus can’t chainload bootloader from disk.
Workaround #1 (see link above): Replace GRUB2 binary on TFTP server and add connectefi scsi to global GRUB2 template
Wordaround #2 (only VMware): Set efi.quickBoot.enabled = FALSE for VM