Couple different things:
Usually the beeping and lights is a low battery, as you stated you have been charging the battery. Did you ever run the battery to completely dead? As that may have caused damage to the battery may leading to replacement.
The other option is that it needs to be re-calibrated by doing the following (from operating manual)
* Make sure you have hover board on flat/even surface
* Mats should be even with eachother not tilted forward or backward.
* Press and hold the on/off button for 15 seconds. Scoot will turn on.
* Turn the board off and then turn the board back on.
* Press power button twice and it should be calibrated