GridPlus Error

Hi All,

I am getting the below error at the bottom of interface canvas when configuring the GridPlus component. I am on Appian version 25.2.

Error: SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

Use case: An user input grid where user can copy and paste large data set from excel 

I have followed the documentation and all the expression rules(queryRuleName, columnConfigs) are working individually. Any guidance will be appreciated.