I have the exact same problem from my Windows 10 machine running Chrome v64 at work. I contacted support, but even after a couple weeks, the devs have been unable to reproduce the issue.
I do have AdBlock Plus enabled by default, but for this debug exercise, I had tried whitelisting app.rach.io and even completely disabling the plugin, but it still just gets me the ‘Error loading data’ message.
I responded to the helpdesk that it is not a “critical” issue for me, since the iOS app is running fine and so is Safari on iOS. Maybe there is some unknown blocker application on our work network, but I can’t explain why it only impacts Rachio’s site, and not my other IOT products (e.g Philips Hue, Ecobee, etc.)