Okay, I solved it. This is what worked for me.
I purchased my XP-15000 printer in January 2022. My firmware version was NW07K7.
1 - Turn off printer
2 - Press STOP, LEFT, DOWN, and POWER to enter firmware mode
3 - Flash INKCHIP firmware (NW99Z9) to 100%
4 - Unplug the power
5 - Plug the power and turn on. Printer enters Recovery mode
6 - Flash the INKCHIP firmware again
7 - Printer shutdown by itself after reaching 100%
8 - Turn on printer and run INKchip activation program
9 - Immediately click the ????? button on the top left of activation program window (I believe this stops the scanning)
10 - Hit refresh and wait a few minutes to see if the printer populates in the drop-down box
11 - Once it's available, purchase the key online
12 - Click on "Activate online"
13 - Paste the code and activate!
Those are the instructions that worked for me. Your experience may be different.