Websites developed by inadequate developers are often only tested in the most basic configurations. The form may be breaking because of some non-standard setting on your browser, and could start to work for you if you change your browser & its configuration to match what those developers expect.

You could try the following...
Try the form again after disabling any adblocking or anti-virus browser addons. Also make sure your browser is not blocking cookies/third-party cookies. If that does not work try another browser (i.e. if you use chrome, try the form again in Edge or Firefox).

If all else fails & you yourself are a software developer, there's always the option of firing up the debugger & bludgeoning the form into submission.