Unholy DK: Epidemic broken

I’m running into an issue that is making my DK unplayable.
When I try to use epidemic I on and off get a “There are no valid targets within range” message and the ability is unusable.

I’ve restarted the game.
Restarted my whole PC.
Ran the repair tool.
Removed all addons.
Deleted the cache.

I constantly have this issue. Send help!

Ok so issue is that you haven’t used outbreak or unholy blight to infect target with virulent plague I had same exact issue felt dumb when I didn’t dot the target first