Thank you
I hope you made the 5 Volt test at the beginning.
When the LYNX powers on, the minimum you have to see is static on the 3.5" LCD. If not, please check the power wires +5 Volt and GND. If you mixed them up, the LCD mod was damaged.
If the power wires are correct, please check the voltage with a multimeter at the voltage regulator: One pad should read 5V (input), one pad 3.3V (output) and the other pad is GND.
Please also check the wires CL2 and RES.
If you also soldered the backlight wire, please desolder it for testing.
Perhaps you can post some pictures of your wiring.