@jikemin same here.
Exactly same problems:
No keyboard input in ipxe menu.
(and no autoexec.ipxe too but i created the file as @AxeMeAQuestion22 did)
With computers:

• Dell OptiPlex 3040 Bios 1.20.1 (last update)
• Lenovo Thinkcentre M910T Bios 1.5A (last update)

iPXE version (1.21.1+)
Fog Version 1.5.10.1660
Kernel Version 1.5.10.1660

Thanks