#NAME? error

Can someone help with the #NAME? error? I cannot find the error in my formula/syntax and need help. I have this on a calendar excel template and need the days of the month in the tops of the boxes. Here is the formula giving the error : =DaysAndWeeks+DATE(CalendarYear,1,1)-WEEKDAY(DATE(CalendarYear,1,1),(WeekStart="Monday")+1)+1

This formula has worked previously in this same calendar, but this error happened after downloading it again from google drive. Thank you for the help in advance.