I think some others said that they solved this by removing the old version completely, then installing the new one. That worked on my forum.
I also still had the problem with the holidays and birthdays starting and ending 5 hours early (based on UK/GMT time, not my US East coast GMT-5) time. So I went in to Development Mode in Xenforo, edited the cron that updates the holidays, and changed it from running hourly to running at 5:01am. (which is actually 00:01 my time, just after midnight) That addressed the problem I was having with the schedule.
I do love this free add-on! I also reduced some of the intensity of animations (like amount of snow, amount of bats). They put a nice setting for this in the settings.
Example: appearance -> holidays -> christmas -> effects -> snowflakes -> snowflake count -> reduced from 200 to 25 -> save