RGB MacroPad won't go into Bootloader/Flash Drive mode

Sorry, could you clarify / rephrase perhaps? No keys work at all? Do internal keys work, such as BL step keys & the RGB control keys shown on the default keymap?

And do you still have the default keymap?

There are alternate ways to get into bootloader mode, but if nothing is being passed to the computer, then that’s a bigger problem.

Alternate macropad bootloader methods:
The macropad shares code with the numpad, so the numpad method of “Hold down keys for 2 and 6 while installing the module” works.
Bootmagic reset to bootloader, Hold numlock key (row 2, column 1 key) while inserting the module.

     *         ┌────┬────┬────┬────┐
     *   row 1 │Esc │Calc│ =  │ <- │
     *         ├────┼────┼────┼────┤
     *   row 2 │ Num│ /  │ *  │ -  │
     *         ├────┼────┼────┼────┤
     *   row 3 │ 7  │ 8  │ 9  │ +  │
     *         ├────┼────┼────┼────┤
     *   row 4 │ 4  │ 5  │ 6  │ +  │
     *         ├────┼────┼────┼────┤
     *   row 5 │ 1  │ 2  │ 3  │Entr│
     *         ├────┼────┼────┼────┤
     *   row 6 │ 0  │ 0  │ .  │Entr│
     *         └────┴────┴────┴────┘

Last option I can think of, the qmk_hid tool can trigger bootloader mode. github.com/FrameworkComputer/qmk_hid