DAX problem after changing data source

[Sohan]

I have the following DAX code in my PBI file. I have only changed the data sources from .xlsx files to .csv files. All the data and datatypes are identical. After changing the data sources though, this code gives me an error:

MAX_User = 
CALCULATE(
    MAXX(
        ALLSELECTED('CALC NP''s (Unique)'),
        'CALC NP''s (Unique)'[User]
    ),

    GROUPBY(
        'CALC NP''s (Unique)', 
        Date[Week],
        'CALC NP''s (Unique)'[Patiëntnumber]
    )
)

For 'Date[Week]' it now suddenly says 'Parameter is not the correct type'. Does anyone have an idea of why this is? 

[amitchandak · Accepted solution]

@Sohan , Check your relationships. I think that has broken, It may happen when changes sources from one type to another

[Sohan]

Thank you so much! The relationship was indeed broken for some reason.