Firefox is already at the version Patchmypc is requesting to update it to. Related question: How can I permanently remove an app from Patchmypc?
CORRECTION -- Firefox (Help -> About) showed version 58.0.2 as "up to date", however Patchmypc was really pointing to Firefox version 59.0. The problem appears to be with Firefox, not Patchmypc. Firefox does not know about a new version of itself that Patchmypc knows about. How weird is that???
Sometimes there channels stage out updates so you may not be getting it yet via their self updater.