PowerBi Doubt Receiving error

In PowerBI learning video i am practicing 11th Video, when i am practicing the session i am receiving error in date check i have added new column and mentioned (Date check = IF(Merge1[Date]>DATE(2019,6,1),"After","Before") formula receiving #error sheet name is correct. Before this i didn't received any error in date, month and day formulas date & time formula also didn't received error. NOTE: Kindly check as soon as possible, i have attached screenshot and give me reply as for previous doubts i didnot received any response.