When I type something in the Search Bar and hit Enter, nothing happens. Nothing also happens when I click on the magnifying glass. I can type something in the Awesome Bar to search, and that seems to work fine.
Start Firefox in Troubleshoot Firefox issues using Safe Mode to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).
You can also try to delete search.sqlite and search.json in the Firefox Profile Folder
That happens when a Adobe pdf file is open in a firefox tab. Close down the pdf and try again.