I recorded a scenario in a GWT application and when I run it for "virtual user validity" it gives me "NL-PLUGIN-ENGINE-03" errors. How can I fix this.
When you record transactions of any web application, there are some parameters with values involved. Those values were used during the recording but most of the time they can't be used anymore to replay the script.
It's what we call dynamic parameters. You have to correlate them by extracting the value from a server response.
Your NL-PLUGIN-ENGINE-03 eror is probably related to that. That error means that NeoLoad was not able to convert the content of the response to XML. It can be the case where the server did not send the expected response.
Please look at NeoLoad documentation here to know how to handle such situation.