First check if tableau recognises both fields as a date.
You can also try wrapping both MONTH values in an INT function - however the MONTH function actually returns an INT so I suspect that alone may not work.
I checked the format of both the date fields, both fields are in "Date" format.
Also tried wrapping both Month Values in INT function but it didnt work.
May be am missing something?
TRY TO WRITE CALCULATION SOMETHING LIKE THIS: ATTR(MONTH([Order Date]))= MONTH(ATTR([Sample - Superstore_Modified (copy)].[Order Date]))
If date fields are used in the calculation, they can be aggregated using the MAX(), MIN(), or ATTR() functions. In most cases, these aggregations will not impact the results of the calculation.