Guessing by process of elimination (of hair on head).
You can do this the hard way or the easy way. Your choice...
Google USB METERS then GOOGLE USB (to whatever) adapters are needed to connect to the phone or other gizmos. These things are CHEAP and worth their weight in gold.
Plug the USB meter inline.
Tah-Dah!
Is voltage anywhere NEAR 5.0 volts when connected to your device?
GIZMOS have a threshold voltage a bottom voltage limit below which they will not work. It isn't the wall wart - it is the gizmo.
I have an LED floodlight charger that does the very same thing. Not the wall wart the controller within the floodlight.
