This message appears when the data you have used in your most recent run has changed format since you performed your configuration from sample data. For example: a field that was a decimal is now text.
This error can be resolved by checking if the format specified in the data inputs matches the format of the column in the input file. If this issue persists, setting the data type to text in the data inputs menu and transforming it using NRL in the match fields will clear the error.