How to do the equivalent of sumif using a date that matches a date from a separate table in power bi

I am trying to sum a row based on matching dates from 2 tables in power bi. The goal is to have both dates match from each table with the new column provided the total count of distinct records based on the date example sumif

[Failing code] (https://i.stack.imgur.com/vobAh.png)

Just establish a relationship between Table1 and Table2 on the date columns, in the relationship view. This should be a relationship with Table2 on the one-side of the relationship, and Table1 on the many-side. This way, Table2 can pass filters to Table1.

After the relationship is established, simply add a calculated column in Table2:

Sumif = 
CALCULATE ( SUM ( 'Table1'[Count] ) )

You can also add a simple measure:

SimpleSum = SUM ( 'Table1'[Count] )

And add this to a table visual together with Table2[Date]. This will also give you what you are after, without having to persist a calculated column to your data model. Unless you are planning to use the added column as a slicing dimension or a category, you do not need to persist it in your datamodel, and using a measure is the best practice.

Edit: Your original DAX code is throwing the error you see because you haven't closed your FILTER function with a parenthesis. The correct code is:

Col =
SUMX (
    FILTER (
        'acumatica wv_install_revenue_nopids',
        'acumatica vw_install_revenue_nopids'[Revenue Recognition Date] = 'Revenue Recognition Date'[Rev_Recog_Date]
    ),
    'acumatica wv_install_revenue_nopids'[Confirmed]
)

I suggest you start formatting your code systematically to make this easier to spot - and I would recommend avoiding ridiculously long table names like acumatica vw_install_revenue_nopids - makes it even harder to spot mistakes.