Microbit blinky (and other code) won't compile using developer.mbed.org

I’m using developer.mbed.org online compiler. I’m trying to compile even the most basic programs for the BBC Microbit and I get a failure with
Error: The build system did not finish successfully. error -230
This worked fine last week (along with all the other programs I had prepared for a class). What’s happened?

Hi Frank,

We’re sorry but there was an issue building projects for the Micro:bit but that was fixed with the Mbed OS v5.10.2 rollout that occurred this week. Could you please try building your project again?

We apologize for the inconvenience and down time that you had to experience.

Ralph, Team Mbed