SUMMARIZECOLUMNS function - date to year month

[Anonymous]

Hi community,

I have the following evaluate statement in Power BI report builder and want to get date to show as "MonthName - Year" format

EVALUATE
SUMMARIZECOLUMNS (
    'PMC List'[PMC Name],
    FORMAT ( 'Dimension Date'[Date], "mmm-yyyy" ),
    'Monthly Line Item'[Contracted Amount]
)

However, I am getting this error and dont know what is wrong. I appreciate for any feedbacks. Thanks!

TITLE: Power BI Report Builder
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Query preparation failed.

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ADDITIONAL INFORMATION:

Query (4, 14) A single value for column 'Date' in table 'Dimension Date' cannot be determined. This can happen when a measure formula refers to a column that contains many values without specifying an aggregation such as min, max, count, or sum to get a single result. (Microsoft Analysis Services)

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BUTTONS:

OK
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[lbendlin]

EVALUATE
SUMMARIZECOLUMNS (
    'PMC List'[PMC Name],
    FORMAT ( 'Dimension Date'[Date], "mmm-yyyy" ),
    SUM('Monthly Line Item'[Contracted Amount])
)