I have a similar / same one I purchased from Banggood. It works fine for me. It is indeed a:
18650 Battery Charger
3.7V to 5V boost converter
an over charge over drain circuit.
When I first got mine I plugged in the 18650 (be very careful about the polarity. I followed the board printing but on mine the battery holder was in backwards so the markings on the holder were reversed.
I then let it charge the battery until the Green Charged light lite.
Did you check the on off switch was ON?
John