PXE-E32: TFTP open timeout (ThinManager)

I have 3 thin clients that won't network boot. I get a tftp time out error.

Has anyone ran into this?

Thin Manager says on there website:

PXE-E32: TFTP open timeout

Using a standard DCHP server with boot options
Verify that there is not a firewall preventing the client from downloading the boot file
Verify option 67 is set to acpboot.bin
Check that acpboot.bin is located in the ThinManager installation directory (default of %PROGRAMFILES%\Automation Control Products\ThinManager)

Hello,
same situation for me, with Thinmanager as well. I use a router to "NAT" some IP cameras, but this router completly disturb my PXE boot devices = TFTP Timeout... I I remove the NAT (or ARP in my NAT), everything is fine, but I lose all my IP camera connections.... How did you manage it ?? any feedback ?

I ended up going to services in the control panel and restarted the service called "ThinServer" on the machine that was listed as the DHCP server. For some reason restarting the VM did not work, but restarting that service did.