Plugin doesn't seem to be compatible

I am a new user to this plugin, and as of now I am trying to integrate it with one form and send the result to the given test link. However without fail upon submitting the form I receive “error code” (or whatever Failure message I input), the form does not submit, and I receive no email from the debug mode. Has anybody else encountered this?

For the record, my Ninja Forms version is 2.9.50.

https://ww.wp.xz.cn/plugins/forms-3rdparty-integration/