Try plugging your watch into a pc/mac running GE and linked to your account. Then unplug it. It seems to make sure the app store knows what FW is on your watch.
There was a new version of the app store launched today, so you might be seeing issues due to that. Base on what you're trying to install, go to it's app store page, and try "contact developer", as there could also be something specific to that watch face and that would be the best place for an answer...