I am no longer receiving calendar notifications for events which are entered as "all day" events on my Google calendar. I had a similar problem about three years ago when I wasn't receiving notifications for ANY events on my Google calendar. I attempted to solve this problem in a similar fashion by uninstalling/reinstalling Thunderbird then disconnect/reconnecting Google Calendar as discussed in the following link, but the All Day events' notifications still are not appearing. https://support.mozilla.org/en-US/questions/1397571 As a debugging step/temporary solution (so I don't miss notifications), I have integrated my Google Calendar with Outlook, and am receiving notifications correctly with that app, so the problem doesn't appear to be on the Google end.