How to lock a formula to a specific cell?

I have a problem. Can you help?

Zapier automatically inserts a date in Sheet1. When this happens, a new line is created.In sheet2 I have used the formula = WEEK.NO (. I have inserted the formula in all cells in column A in Sheet2.But every time Zapier inserts a new line in Ark1, the formula moves in Ark2 column A. How to fix it?

I have used $ in the formula. But that does not solve the problem.

Here is a link:

https://docs.google.com/spreadsheets/d/1_zi0Ze79jK_R_IBfKRdC8YM29h7aJWKvcsUWZ2IwxkU/edit?usp=sharing