Cannot Program Bootloader

[WN7D]

Bought the radio mid-March 2025. I was able to Upgrade the FW (I think). In any case I was able to program my call sign into the unit AVRDUDESS vers. 8.0. When I power it up my call sign shows up but not the FW version.
I have been trying for a couple of hours to install the bootstrap loader per what I've read here. I am using a known good cable and following the instructions and settings explicitly. No matter what I do, it will not work. It clicks and blinks shows "error programmer is not responding" "...not in sync: resp=0x00".

Any advice would be truly appreciated.

[DL2MAN]

Bootloader can only be programmed via ISP Header, using a programming device (like Arduino Uno).

[WN7D]

Thank you for the fast reply. I was afraid of that. That leaves me out. In the meantime, How can I verify the FW version?