A circular dependency was detected

Hi timward10  -Modify your measure to ensure Assay Month is correctly compared as a string

Assay Cumulative Count =
CALCULATE(
COUNTROWS('EXENT Funnel - by Product'),
FILTER(
'EXENT Funnel - by Product',
FORMAT('EXENT Funnel - by Product'[Assay Month], "MMM yy")
IN {"Jan 24", "Feb 24", "Mar 24", "Apr 24", "May 24", "Jun 24",
"Jul 24", "Aug 24", "Sep 24", "Oct 24", "Nov 24", "Dec 24"}
)
)

another options, If Assay Month is stored as a date, then compare it using YEAR() and MONTH()

Assay Cumulative Count =
CALCULATE(
COUNTROWS('EXENT Funnel - by Product'),
FILTER(
'EXENT Funnel - by Product',
YEAR('EXENT Funnel - by Product'[Assay Month]) = 2024 &&
MONTH('EXENT Funnel - by Product'[Assay Month]) IN {1,2,3,4,5,6,7,8,9,10,11,12}
)
)

Hope this helps.

Hi timward10 

A circular dependency error happens when a column or measure indirectly refers back to itself, which creates an endless loop. In your case, it’s likely because “Assay Feb 25” is built on “Assay Jan 25”, and that column already depends on another calculation, forming a cycle. The IF condition in your formula may also be pointing to fields that are tied together, which adds to the problem. To fix this, you’ll need to break the chain for example, by creating a helper table, avoiding direct references between dependent columns, or using a lookup table for date-based logic. A better option in many cases is to use measures instead of calculated columns, since measures calculate on demand and don’t create stored dependencies. You can also check the Dependency View in the Model tab to see where the loop is happening. If it’s still hard to trace, try building a simpler version of your formula first and then add complexity step by step until it works.