Hate to answer for another but the step he was missing
was to press and hold SET until the radio was ready to
rx or tx data. He was half way there by holding down the MHZ key while powering up. Then rotating the channel knob to F7 CLONE.
Now he can press and hold the middle button BAND/SET until the
display blacks out and then release the button and the display
comes back with CLONE. He was missing that step. Now he can set his
software to rx or tx data and then hit the appropriate button on the
radio to start the transfer. TX or RX will appear on the display depending on what he wanted to do. The last time I programmed my FT8900 which is nearly identical in setting it up to clone I too forgot to
press set. On the 8900 you just press it momentarily. the 7900 you press and hold. That is what Joe was referring to down at the bottom
of this message. More than a momentary push of SET on the FT8900 will cause the transfer to fail. I'll have to give that a try to see what exactly happens.

Milton