No sound on Firefox 57.0.1
I get no sound at all on duolingo on Firefox, but other websites have no sound problems. I'm on Windows 10, latest update, if that matters. Help!
Have you tried other browsers such as Chrome?
If another browser works, then try deleting your history / cache.
You can also check to be sure you haven't disabled audio - hover your mouse over your name, then click "Settings" and make sure the speakers are enabled.
If none of that helps, you can report a bug. Here's how: https://support.duolingo.com/hc/en-us/articles/204728264-How-do-I-report-a-bug-
What buttons, what sound.
There are multiple ways to access an exercise: global strengthen skills button, strengthen skill from within a skill, re-do lesson, etc.
Please try exactly to explain where you want to click on.
My tests have shown, that there are so MANY side dependencies: https://www.duolingo.com/comment/25364990
Try to downgrade to Firefox V52.5.0; this works partly for me on an older Windows OS version; at least with the "single strengthen skill - not the global skills".