My Apple Watch will not charge. Could it be the charger?

That could be the reason but here are other possible reasons:

If your Apple Watch won't charge or it won't turn on - Apple Support

• Check connections
• Check cords for damage.
• Try using a different outlet or different charger and cables
• Try reseating the watch on the charger
• Clean charger and watch
• Restart your Apple Watch, and then try charging again

Try a different charger/wall outlet and if it's not that it might be worth having the battery checked out at an apple store.