I have a MightyHat on a Raspberry Pi Model 3 A+, but the backlight does not stay on. The R2 general purpose pushbutton does momentarily flash the backlights as it is cycling thought the LCDlight percentage menu, but I can't figure out how to keep the backlight on.
Any help would be really appreciated.
That should keep it on at whatever percentage the LCD shows.
It's just a PWM signal from D3 to the LCD backlight.
I would check any solder joints on the LCD header, maybe some DMM continuity check from the atmega pin to the LCD backlight. See the schematic (https://lowpowerlab.com/guide/mightyhat/cad-enclosure/).
Thank you Felix, Your suggestions worked. It had a bad solder connection on the LED pin.