Trying to show a message on a card if there are no new records in last 7 days

[JPBR549]

Hi all.  I'm new to Power BI and DAX.  I'm working on attempting to use a measure using DAX that displays  the message "No new registrations in the last 7 days" if there are no new registrations in the last 7 days, but not having much success.  The DAX Code I am using is:

NoRegistrations = if(ISBLANK(DimCompany[registration_effective_date]>=Today()-7), "No new registrations in the last 7 days","")

The error message I am getting is "A single value for column'registration in table 'DimCompany' cannot be determined.  This can hapened when a measure formula refers to a column that contains mny values without specifying an aggregation such as min, max, count, or sum to  get a single result.

Thanks in advance for assistance.

[JPBR549]

I was able to fix the issus using 

New Registrations = IF(ISBLANK(Calculate(Count(DimCompany[Registration_Id]), Filter(DimCompany, DimCompany[registration_effective_date]>=Today()-7))), "No new registrations in the last 7 days","")