Electron stops being OTA flashable

I have an application running on an Electron in the midst of debug and development.

I have successfully been OTA downloading and the Electron has been successfully publishing to the Cloud.

Suddenly, I can no longer OTA flash the Electron. It continues to connect to the cloud, publishing data. The web IDE claims flash is unsuccessful and the Electron never flashes magenta (though does rapidly flash blue as the attempted download happens).

Thoughts?

That is odd, as the download would also flash magenta and not blue. Blue should not happen at all if not in Listening Mode.
Or are you actually seeing it flash cyan? (like breathing cyan, just quick on/off)

For the OTAing
You code might interfere with the download (e.g. longish loops, delays or actions that occupy the modem or serial ... hard to say without seeing your running code).
But try putting the device into Safe Mode and try OTA again.

BTW, OTA flashing does suck up biggish chunks of your data quota.

I do think there is something else going on. Particle Dashboard reports the unit as being online … despite being powered off for the last two days.

This is a known issue related to the fact that Electrons use the connectionless UDP protocol while the WiFi Particles use TCP which allows for online testing.
For the Electron a permanent ping would suck up your data quota.