Google Nest apparently removes the option in our Google Nest app when the holiday is over. When it's available, it appears under Device Options under Settings. (I found this on another site.) Their site says Google Nest changes it back to "Ding Dong" automatically when the holiday is over.
Google Nest must have a bug on their server, then. Google Nest Help (https://support.google.com/googlenest/answer/9231819?hl=en#zippy=%2Cdoorbell-theme) claims this:
"After the holiday, your doorbell automatically goes back to the default tone, and the seasonal theme disappears in the app."
Thank you for all of your patience while dealing with your missing doorbell chime! Have all of you made sure that you have fully restarted your devices first? I would like you to try to restart it first.