Sololearn.com Runtime Error?

Question

https://gyazo.com/c44c2734d995c501fa9f1aa57ea9e31d
Getting this error when trying to visit the Sololearn site. Seems to work in Chromium but not Firefox.
OS: Windows 10
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Edit: Doesn't work on Waterfox either, (A Firefox based browser). Hopefully this isn't a problem on their end and I'm just having some sort of issue with my Firefox setup.

Answer 1

Maybe they are updating something. So website can't be work sometime. Check after some time.

Answer 2

It's been 2 hours, I've reported this as a bug.