Date aggregation lastdate vs max

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Having an issue here with displaying the max date for each row in my matrix

When adding the date column as a value, it only gives me to aggregate it to count or count(distinct)

When trying to create a measure with lastdate e.g. LASTDATE(qualifications[valid_to_date]) it gives me an error "An invalid numeric representation of a date value was encountered"

When trying to create a measure with max e.g. max(qualifications[valid_to_date].[Date]) it gives me the max of the whole table rather than just the row

In the query editor the column im trying to aggregate is defined as Date/Time

Does anyone know where i'm going wrong? Any help would be appreciated