Can't comment on Instagram
There seems to be an on-going issue with Firefox 23 update.
People can no longer comment or like images on the Instagram website.
All the issues are described here:
https://support.mozilla.org/en-US/questions/968174#answer-487341
Όλες οι απαντήσεις (1)
The issue with Instagram's script for showing images not working in Firefox 23 is discussed in this thread: Unable to view photos on Instagram properly.
These other issues could be related. Unless you have seen something new, this is due to a change if Firefox that Instagram needs to respond to by changing its script. I have not seen a working solution for end users on this forum. (There might be something on a support forum at Instagram, if they have one.)
By the way, are you sure you want the Zoomex extension? A Google search turns up numerous pages on how to get rid of it because it inserts ads into pages. You might consider disabling it here:
orange Firefox button (or Tools menu) > Add-ons > Extensions category