Firefox status tab?

I moved my bottom panel to the side of my screen but did not like it there so I moved it back to the bottom.

But something changed- When I open firefox it no longer appears as a running tab in the bottom toolbar.
If I minimize firefox it no longer reduces to the bottom running tab so I can click on it to maximize it again.

Instead it simply vanishes when I minimize the firefox window.

How do I make firefox appear as a running tab in the bottom taskbar again? I'm running 8.10