Unfortunately you are probably beyond the 12 month warranty period for Cygolites. You can opt for sending it in for repair. Information here: https://cygolite.com/warranty-and-repairs/ You must have the original sales receipt for warranty services.

It could be the battery or it could be the charging components in the light. That is a rather short lifetime for a light that sells for $33 to $50 depending upon where you buy it. Lithium polymer batteries are usually rated for 500 recharges before the capacity drops to a point where the light is less useful. Sending it in and paying for repair and return may be more than the light is worth.

It's why I have been a fan of the cheaper USB rechargeable lights. If you spend $5-$10 on a light and it fails after a year, it's no big deal. Losing $30 to $50 is a big deal for me.