Hi   !
Could be that   CBS   isn't doing the required coding for Firefox.
Maybe you already tried this,   but you could ask   CBS   why these buttons aren't showing:
www.cbsnews.com/contact-us/

I don't see the video controls either. Not with Firefox 50, nor with an older Firefox 38.7.1 ESR version I have installed. Happens with another browser based upon Firefox, too - SeaMonkey.

IMO, that is CBS doing that, because I also get an extra "mask" or border that I don't see in Vivaldi; which is very similar to Chrome and uses the same Flash Plugin that Chrome uses. I don't have Chrome installed, because I consider Google as the "empire of evil".

I haven't seen that "glitch" at any other website that uses Flash, when using Firefox or SeaMonkey. No extraneous "mask" or border and the video controls for Flash appear everywhere else, as expected.

I don't have   Chrome   installed either,   but when I use   Edge:  buttons are there   .......
CBS  might need to change their coding for Firefox   .......

I believe Edge nay use the same Flash PPAPI plugin that Chrome and Vivaldi use. Might be difference with the Flash plugin being used, but my bet is on page coding considering the "mask" or "border" that appears above the Flash inner window that I see in Firefox.