Please ensure that you are using EVOVE's magnetic charger that comes within the product's packaging.
Also be sure that:
a. the EVOVE charger is connected to an adequate USB power outlet,
b. the battery device's charing pins are well connected to those on the charger.
If the issue persists, please try cleaning the connection on both the battery and the charge with a piece of paper/cotton dipped with rubbing alcohol.
If then the issue remains, please retain the product and contact EVOVE Support Team at email@example.com.