I can’t see your graphics card in the blocklist[1] so I’m not sure why hardware acceleration would be disabled. If you look in about:support is it definitely not working? If you go to about:config and search for ’acceleration’ is anything disabled there?

If none of that works, you could try going back to about:support and click on Refresh Firefox. You’ll lose settings and extensions but it can clear up problematic issues. [2]

[1] https://wiki.mozilla.org/Blocklisting/Blocked_Graphics_Drive...

[2] https://support.mozilla.org/en-US/kb/refresh-firefox-reset-a...