Sorry about the error you're getting.
I just tried this challenge, and am not getting any errors. I also entered a couple incorrect attempts inadvertently, and still didn't get any such error.
It's a backend code checker, likely a Docker error, although not sure what would've caused it; this may've been temporary, perhaps some sort of glitch.
If you can still reproduce this, can you
- post the code you were submitting, and
- a screenshot of this error occurring. Make it of your entire browser, please.