Describe what happened
A useful report includes whether you were hosting or joining, what you were doing, and the steps that caused the problem. Note whether the other player saw the same behavior.
If you can reproduce the issue, record the shortest sequence of steps. Include any error message shown by the launcher.
Send diagnostic logs
The beta launcher has a Send logs button. Use it after reproducing a problem to submit selected diagnostic text and version information. Sending logs is a manual action; visiting this website does not submit game logs.
Follow the instructions supplied with your beta build for setup and testing. Read the privacy page for information about website services and diagnostic reports.