Video Doorbell 2 went dead in 2 days after installation

Hi there,I live in Chennai, India. I installed Doorbell 2 a couple of weeks ago in June 2021. The instrument was bought in the US and gifted by my daughter in 2018. The installation was quite smooth and I followed the instructions to a T. The instrument worked fine EXACTLY for two and a half days and went offline. I thought the battery's initial charging might have been inadequate, hence charged it fully once again, and tried to start the instrument, but no joy! The doorbell won't start. Absolutely no sign of life at all. I then tried resetting the instrument as given in the manual and here in the discussions, but to no avail. The dead instrument remained dead with no sign of any activity. The battery charges OK and retains the charge as well. But, I noticed a strange behavior: When the battery is left in the dead instrument say for overnight, it still seems to drain quite fast!! Don't know how a dead instrument can drain a battery! This draining I found out accidentally - when I tried to check if the battery perhaps may need some topping up of charge for my next try to revive the instrument, it once again takes some 1-2 hours to charge to full.! Don't know how to interpret this.I still cannot believe a brand new instrument can go dead taking the battery charge along within 2+ days, even though I tried to use it only 3 years after purchase.Any help in reviving my instrument will be much appreciated.Thanks in advance.