I'm doing an evaluation. I have recorded a few steps but it wont play back to to this error and the documentation doesn't seem to help. I dont know the first step to try and resolve this.
That errors is related to Oracle Forms so i guess you are trying to replay a script against an Oracle forms application.
That error is generic and it can have multiple root causes. Basically, the server sent a response to a request that cannot be desirialized.
As you may know Oracle forms protocol is a binary protocol. NeoLoad is decoding the requests/responses to an XML format so you can understand their content.
Here is some tips that hopefully will help you to troubleshoot that issue. First of all, make your script as simple as possible like a login-logout. Then try to replay it. If it works then you can record the same with one more transaction.
Usually on Oracle forms application, you have to handle some dynamic parameters in the beginning of the script related to the login. Did you manage to handle such parameters?
Compare the responses sent during the validation before that error. Make sure that they have almost the same content. If not then it means that you did not send the right content probably using recording values instead of the dynamic ones.
Also you should look at the NeoLoad documentation here to understand how Oracle forms testing works.