How can I completely reset iMessage in Yosemite?

I'm experiencing issues sending iMessages from my Mac. It used to work, but stopped. I tried a bunch of "fixes" I found online:

• sign out of iMessage and log back in another day


• rebooting


• restarting my phone

None of these worked to resolve the problem.

I tried to reset the Messages app by removing some .plist files, but that didn't work (those instructions are from 2012).

I'm running Yosemite 10.10.2. How can I reset the Messages app to a blank slate?

[EDIT Sat, Feb 14]

I also tried setting up Messages using another user account on my Mac, and it worked flawlessly. This leads me to believe there's some kind of issue with iCloud syncing between my iPhone and Mac.