Included in Missing e 2.12.0 is a fix for the Magnifier feature that stopped working earlier today. The fix I’ve implemented is not 100% tested, but I wanted to get something working out to you sooner.
I’ve also made a few other small fixes, including improving the spacing of wrapped tags that was affected by a recent Tumblr change.
A recent change to the Firefox tools that are used to create this extension have caused Missing e to be no longer be compatible with Firefox versions below 13. I will look into this to see if I can restore backwards compatibility, but it is worthwhile to keep Firefox up-to-date anyway. You should be able to update Firefox from your browser’s menu.