From https://support.mozilla.org/en-US/questions/1369731#answer-1487157

"Javascript is enabled by default. If you want to check, open a new tab, enter about:config in the address bar, accept the risk and search for java. The preference is javascript.enabled."

Make sure javascript.enabled is true. If it is not, double click on the bar to do so.

how to turn on java script in Firefox

JavaScript is enabled by default in Firefox. There are a number of extensions that you can install from addons.mozilla.org that can affect how JavaScript works in Firefox such as NoScript,

Also according to your More system details on right it looks like you are not displaying a web browser UserAgent to this web site for some reason so I wonder if that is the issue. https://support.mozilla.org/en-US/kb/how-reset-default-user-agent-firefox