If the TFTP server is Windows standard (which is WDS based) you might have tried to use a path or file extension which isn't allowed out of the box, Verify the ''ReadFilter'' setting [[appnote:chainload_wds|see this old but still relevant documentation]] and that it allows what you want to load. For example ''autoexec.ipxe'' might fail due to ''*.ipxe'' which is the standard name for iPXE scripts, is not allowed.