What is your data source? Please go to Power BI Desktop query editor to check the APPLIED STEPS and check if which step throws this error.
In addition, please go to Advanced Editor of your current query in Query Editor, then check if the file path is correct.
i am connected to a folder, where i have 3 excel
i have used edit option to combine that 3 excel together, after combining when i am applying the changes
i am getting this error, i checked the step and noticed that row 2 is coming as error(See below)
[Expression.Error] The key didn't match any rows in the table
Would you mind sharing the Folder through Private Message? I will test it in my Desktop.