Edit: ahhhhh, you added a pull request. Missed that. Very nice.
So I went through it, and found you were accessing Ride.buildDate, but that property doesn't exist in the API yet. The age says "undefined" when I use the plugin with an OpenRCT2 version I downloaded earlier today (v0.2.6-3260979).
Here's the un-minified code: [redacted at OP's request]
also, I think you did a nice job with the window. It looks much nicer than the demo window from the reload example video.