Syntax error: data type isnull does not match a defined type name

The sample date in my table is like below

and I am trying to make all the blank cells with value "0".

I applied this formula iif(isnull([Daily OH COST],0,[Daily OH COST]) with "formula function" under "in database" .

Somehow the word of "COST" changed to blue color, however, the query did went through and I use the "summary" function sum the result.

However, when I use the "filter function" after that and try to filter out the today's date and Last year today's date (Date-365), I got this message

SQL Prepare SyntaxError: Data type isnull does not match a defined type name

Why this error message shows up when I try to filter the date while I don't have Null in the Date column and the data type is Date.

Here is the formula I used when filtering out the date.

"DATE" = date or "DATE" = date - 365

I also tried  "DATE" = DateTimeNOW () or "DATE" = DateTimeNOW () - 365  and still have the same problem.

Then I tried to change the name "Daily OH COST" to "Daily_OH_COST" then apply the fomula

iif(isnull([Daily_OH_COST],0,[Daily_OH_COST])

Well, this time the word "COST" didn't change to blue color, however this error message still block the query when filtering the date..

SQL Prepare SyntaxError: Data type isnull does not match a defined type name

Could you please help to advise when part is wrong....

Thank you.