I've identified the issues. Initially, I forgot to install a resistor, potentiometer, and capacitor. I was too hasty after checking the voltage to bother verifying if anything was missing.
However, even after installing the missing components, I still encountered the same error: "SID(x) not available (CAN disabled)". I then tried using a different LCD screen, which resolved the issue. I was previously using an Adafruit 499 LCD screen, which I believe operates in 8-bit mode. https://www.adafruit.com/product/499
I'm now using a very cheap LCD screen from Aliexpress, although the display quality is poor. I know I can modify it to use the 8-bit mode but I would prefer for now to go with a plug and play solution.
If anyone has a recommendation for a good LCD screen, please let me know (mouser / digikey).