Minecraft Dungeons launcher quits while loading account

The Minecraft Dungeons launcher starts up, begins to load my account, and quits after a couple of seconds of '...' without giving me the opportunity to launch the game instance.

This seems to have happened within the last 8 hours, as I was playing the game earlier today with no issue. I don't recall seeing the launcher trying to update recently.

I've tried rebooting my system and repairing the launcher using the installer - neither have had any effect.