Thank you for your response.
Yes, I downloaded the pbix file on another (virtual) pc. But we are on the same network and have access to the same databases.
Yes, I can see the new columns when I open PowerQuery - including data. So the updated view is recognised by PowerQuery.
When I go back to the PowerBI report, I can also see the fields in the fields list, but whichever I select, reports an error (as the one in the original post).
What I since learned is that if I open the PowerQuery and see the new colunms then Update/Load the data and then saves my pbix-file and reopens it, it works!
It is a workaround which should not be necessary, but as long as the workaround works, I'm happy 🙂
And confirm: Both users (creator of original pbix and myself) are using newest version of PowerBI Desktop.
/Ole