I get no output from my LD19 when I connect it to a 5V adapter, but I get output when I connect it with a usb.
My guess would be that your ld19 and the development board are not sharing the same GND causing no output from the ld19.
Please connect their GND together to ensure that they can share the same reference potential.
The GND is the reference point for all potentials in the circuit, it ensures that signals and currents in the circuit will flow correctly.
Thank you so much. I run the gnd throw the board and it’s working!!!