The KBD75 was sold through various rounds, with various PCB changes between them.
Firmware files are SPECIFIC to each board. Firmware files from one, will not work on the other.
Make example for this keyboard (after setting up your build environment):
make kbdfans/kbd75/rev1:default
make kbdfans/kbd75/rev2:default
See the build environment setup and the make instructions for more information. Brand new to QMK? Start with our Complete Newbs Guide.