SQL Insert not Inserting

Hi everyone, could someone help me with this mystery? If I run the select query it returns me the results 799 , and 713 so I know the select is returning data. But when I run it as part of an insert statement the table doesn't populate, even though it says its been successful. What am I doing wrong?

"(1 row affected)

Completion time: 2024-03-11T16:32:49.4133365+00:00"

INSERT INTO  I3_IC.dbo.GBR_Filtersize 
SELECT Count(*) , count (Distinct DebtorID) 
--, calldisconnectedtimeUTC
From I3_Dialer.dbo.GBR_CRMSystem a
Left Outer Join I3_IC.ININ_DIALER_40.CallHistory b on  a.I3_IDENTITY = b.i3_identity
Where datediff(day,importdate,getdate()) = 0 and Dial = 1 and campaign = 'GBR Campaign'

The Dial & UniqueDials columns are both INT's

I've just seen it is updating but not on the rows I needed. I think I'll change it to an update statement.