I got Marlin from the main website and configured it using visual studio
You may want to do some searching to see if someone has published a Marlin 2.x / SKR Pro 1.2 / BTT 3.5 / CR10 build that is known good.
There are a Ton of things in Marlin that can lead to things not working.
If you want to keep troubleshooting your own build, then we need to presume that the USB is misconfigured, as well as the UART and config for both Marlin mode (EXP1/2) and TFT mode (UART) interfaces to your LCD.
Until we get some sign of life on one of those interfaces, it’ll be low level troubleshooting and config review.
SERIAL_PORT -1
BAUDRATE 115200
SERIAL_PORT_2 1
BAUDRATE_2 115200
Serial port 3 isn’t enabled?
I got the settings from an older firmware for the CR10 but obviously I’ve also had to change settings for the screen
Thinking about this some more…,
If it were me I would grab the official BTT Marlin 2.x series firmware for the SKR Pro 1.2, and flash that. If your LCD works, then at that point we can at least rule out a bunch of potential other problems and you can start doing troubleshooting on your source modifications.
A couple of leads on test firmware