Have you had colder temperatures? Google Nest has just admitted that it's new battery doorbells and cameras can't recharge at temperatures below 32 F (0 Celsius) and that you may have to let the doorbell or device warm up to room temperature first.
Here is Google Nest Help's new page (new last week):
Here is a CNET story on the issue:
Here is a very long thread in this forum (over 560 replies) on cold weather concerns with the battery doorbell: