I attempted to create a relationship between Locations and Sales after creating a new column in each, CountryZip. I got the error above. I ended up "Sending a frown" to report the error, but I was later able to create the relationship by following the steps, and that is what I want to ask about.
The steps say to create the two columns with the following signature: Country + ", " + Zip. This worked; however, during the Excel course I was able to create CountryZip like this: Country + Zip, no spaces or other characters. Why would Power BI throw an error when attempting to create a relationship between two tables where the CountryZip column is Country + Zip, but not Country + ", " + Zip?