Btw, I notice I have the same issue even with a single database.
IF ISNULL(AVG([Sheet1 (Database1].[Overall rating]))=FALSE
Then AVG([Sheet1 (Dabatase1)].[Overall rating])
This has the same problem mentioned in my original post.
Good morning Swaroop,
Thank you for taking the time to look into this.
I started the workbook this morning, and was greeted by this error message:
"An error occurred while communicating with the data source.
Cannot blend the secondary data source because one or more fields use the == function, which cannot be computed locally."
So I do believe it is indeed a relationship issue between my databases. Now I've Googled this error but I'm not finding any proper solution sadly. It appears it can appear for a variety of reasons.