If Condition for Text not recognizing column name

Hi, Anonymous 

According to your DAX formula and error message, it seems that the problem occurs because of one missing parenthesis in the function LEN(MAX('Sessions'[Known Visitor Id]):

I suggest you to change the DAX formula like this and check if the problem can disappear:

Known Visitor Id = 

RIGHT(MAX('Sessions'[Known Visitor Id]),LEN(MAX('Sessions'[Known Visitor Id])) - FIND("\",MAX('Sessions'[Known Visitor Id])))

And you can get what you want.

If you still have a problem, you can post some sample data(without sensitive data) and your expected result.

How to Get Your Question Answered Quickly 

Thank you very much!

Best Regards,

Community Support Team _Robert Qin

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.