Looking into XSRF/CSRF Prevention in ASP.NET MVC and Web Pages it appears that you're either sending an incorrect __RequestVerificationToken parameter value or completely miss the step.

If the current HTTP request already contains an anti-XSRF session token (the anti-XSRF cookie __RequestVerificationToken), the security token is extracted from it. If the HTTP request does not contain an anti-XSRF session token or if extraction of the security token fails, a new random anti-XSRF token will be generated.

So your test should look like:

• Open Login Page (HTTP Get Request)

  • Extract __RequestVerificationToken dynamic parameter value using suitable JMeter PostProcessor, I would recommend going for CSS Selector Extractor, the configuration would be something like:

    

• Once done you can refer the extracted value as ${token} in the next request

  

Check out ASP.NET Login Testing with JMeter article for more detailed information and step-by-step instructions if needed