Hi @MostafaGamal ,
Have you selected a correct date(existing in your list)?
Can you provide some screenshots your formula using in the DataTable?
I agree with @Anonymous's view, but I am not sure why this doesn't work for you.
I did a test on my side based on your requirement, and everything works fine.
1. Here is my DataTable1 populated from a SP list called "list10" with a Date column called "BoardDate":

2. For helping you find the difference more clearly, I add a second DataTable, and set its Items property to:
Filter(list10,BoardDate=DatePicker1.SelectedDate)

Compare with my steps and check if there is any difference with your step.
Let us know if you still have issue.
Best regards,
Allen