BQ24075: I see the current through the battery but it doesn't charge

Part Number:BQ24075

Hello,

I have an issue with the part BQ24075. I connect an external charger to charge my battery lipo and i can see -450mA through the battery, which mean it's charging. All work fine, but the voltage of the battery doesn't change when it's charging. I tried with different battery but it's always the same. 

Do you have an idea why i can see a good negative current through the battery but the voltage doesn't change? i have no load on the output.

thanks you