Make sure you are not blocking content.

Diagnose Firefox issues using Troubleshoot(Safe) Mode {web link}

A small dialog should appear. Click Start In Troubleshoot(Safe) Mode (not Refresh). Is the problem still there?

https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop

Many site issues can be caused by corrupt cookies or cache.

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Delete cookies to remove the information websites have stored on your computer {web link}

• How to clear the Firefox cache {web link}

Thank you. Running in Troubleshoot Mode eliminates the problem. However, clearing Netflix cookies and cache does not, although the behavior has changed somewhat (the control popups don't disappear immediately as before but do when I try to make a change.)

It could be the work of one of your add-ons, or it could be Hardware Acceleration. How to disable Hardware Acceleration {web link}

Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control> (Mac=<Command>) <Shift> A)

In the Add-ons Manager, on the left, select Extensions. Disable a few add-ons, then Restart Firefox.

Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All Of them.

If the problem continues, disable some more (restarting FF). Continue until the problem is gone. After, you know what group is causing the issue. Re-enable the last group ONE AT A TIME (restarting FF) until the problem returns.

Once you think you found the problem, disable that and re-enable all the others, then restart again. Let us know who the suspect is, detective.

Thanks again.

Rather by accident, I've learned that the issue is linked to use of Subtitles. The control popup disappears when the mouse pointer travels over a subtitle box. The size of the text box appears to vary as a function of how much dialog is contained (reasonable; edges of box cannot be seen) so sometimes it's possible to navigate to the control without mousing over a text box and then the control works. (Netflix seems inconsistent in use of subtitles - sometimes when there is no dialog, there is no box at all; other times, they present a description of sounds, e.g. "dramatic music" or "raindrops falling". Control popup does not disappear when no text is presented.) If Subtitles is turned off, the the control popup does not disappear. I've been using Subtitles recently as a noise abatement solution in a crowded environment. The issue is specific to Netflix, most likely because the arrangement of controls, etc is unique to them.

Perhaps there is a software solution that would allow mousing over the subtitle box but that doesn't seem to be a priority. So you can mark this "solved". Appreciate your help.

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems. Go to that post and click the 'Solved' button to its right.

You should contact Netflix support on this.