UserAgent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:55.0) Gecko/20100101 Firefox/55.0

Example URL:
https://labs.ssbbartgroup.com/index.php/JavaScript_Alert

Steps to reproduce the problem:
1. Launch JAWS or NVDA
2. Navigate to https://labs.ssbbartgroup.com/index.php/JavaScript_Alert
3. activate the alert me button

What is the expected behavior?
text OK should be announced.

What went wrong?
Nothing was announced when Alert me was activated.

Does it occur on multiple sites: Yes

Is it a problem with a plugin? No 

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 60.0.3112.113  Channel: n/a
OS Version: 6.1 (Windows 7, Windows Server 2008 R2)
Flash Version: 

This works as expected in firefox.