Sort:  

It should be working fine on Firefox if you re using the latest version. Can you check which version you are using?
I just connected and used GIF without issue from my Firefox. Uninstall from Chrome Foxified and reinstall it, you must have an old version.

EDIT: Do you use other extensions that might interfere? Because Nothing on my app could post your comment by itself.

I went through the whole process again and it is now working correctly. I just learned that the steem plus button that is added to the steemit UI at the top logs me out, so it's possible I clicked that previously, expecting to get a menu but actually being logged out.

I just tested the GIF inserter. It's a bit buggy, but I did get a Gif inserted at least (for the first time since I've used this plugin and the previous version).

I don't have any plugins that I would think would interfere with steemit, no.

Oh, also, it would be great if you would add Steem Ocean to the list of links that are rendered by your plugin. I will be greatly expanding the functionality there in coming weeks. :)