When I submit REST HttpRequest, I got this error : Error Code: NL-NETWORK-01 Message: Network error: An IO error occurred sending the request. Details: java.io.IOException: http_1_1_required_error Please refer to the documentation for further details and advice Do you have any idea about the cause of this error please ?
In the check virtual user panel hit the Advanced button and select the browser settings. From here you can disable HTTP/2. Could you try a new user validation with that option disabled?
I attached a screen shot that shows that option.