When testing user registration with valid data, nothing happens. What should you do first?

If nothing happens when entering valid data into the registration form, the first things to check are:

• Errors in the browser console (JavaScript errors can block script execution).
• Correctness of the request sent to the server (check network requests using developer tools).
• Proper validation on the client and server sides (the data may not pass validation).
• Server logs for errors during request processing.

This will help determine at which stage the failure occurs — on the client or server — and guide further investigation.