Help connecting Arduino as ISP to PCB

So my stupid self didn't include an ISP header in my project, and I mistakenly ordered and soldered an Atmega328P-AU without the Arduino bootloader on the board. I did include a serial header to program with a serial-to-USB converter, but it's pretty useless without a bootloader already on the MCU.

I'm trying to burn a bootloader to the 328p AU without removing it from the board, so I've carefully soldered some wires in points in the circuit that connect to the corresponding pins necessary to connect to an Arduino UNO as ISP. I've included a picture of my schematic and where I have attached wires to connect to the Arduino UNO as ISP below.

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I continue to get errors that indicate I have a wiring problem, but I'm not sure why it isn't working. I've tried using Nick Gammon's bootloader sketch as well as the "Burn Bootloader" option in the Arduino IDE without luck on my board. Though, I have successfully done both to another Arduino UNO.

Is it possible the pull-up resistor R12 is interfering with the output from Arduino D10? Or maybe the pulldown resistor R8?

I removed the toggle switch, as it either shorted the 328p AU pin 17 to 5V or ground, and the speaker was never connected. I've done continuity checks on my wires to make sure they are continuous with the corresponding pins on the 328p AU.

Any help would be appreciated