Apple Watch Series 6 won’t charge

it displays the time next to a green lightning bolt when it is on the charger. If I take it off the charger the bolt turns red And then goes black. I’ve tried leaving it on the charger over night and it didn’t charge. Just kept showing the time and bolt. I’ve also tried forcing a restart and the Apple logo won’t appear. I know it’s not my charger because it does the same on my mothers charger. And my mothers Apple Watch also charges just fine on my charger