Issue
Unable to import Nintex license.
Error Code
Sorry, something went wrong.
The security validation for this page is invalid. Click Back in your Web browser, refresh the page and try your operation again.
Resolution
To get rid-off from this error message, we can change the web application validation settings in Central Administration > Web Application General Settings Page.
Got to page “Web Page Security Validation” and select Security Validation is “Off” radio button.
Additional Information