The expression refers to multiple columns. Multiple columns cannot be converted to a scalar value

Hi PC2022 ,

Thank you for reaching out to Microsoft Fabric Community.

Thank you techies for the prompt response.

Yes - the error you're getting ("The expression refers to multiple columns. Multiple columns cannot be converted to a scalar value".) comes from this part:

LastCompletedTask & " finished on time"
LastCompletedTask is a table (result of TOPN), and you're trying to concatenate it with text, which requires a scalar value.

I have created a measure called "FirstLateMilestoneTask" in the attached pbix file which can solve the issue, please go through it.

If this post helps, then please consider Accepting as solution to help the other members find it more quickly, don't forget to give a "Kudos" – I’d truly appreciate it! 

Thank you.