I have a 1st Generation ring doorbell I installed in Jan 2020. Been working fine up till now. The battery level shows 100% , the front round light is on, but I get no response from the bell when the button is pushed. Contacts are clean. Could the battery be dead and still show a hardwired 100%. It is hardwired.
Take the battery out and connect it up via its USB cable to see if it charges correctly.
But, yes, batteries can degrade with time and environment it is used in.