Runtime Error on Firefox

Question

I started using Sololearn about 2 months ago and had no problems. I use it between computer and phone often. Yesterday after doing a few questions on HTML I clicked on Code Playground and got this error: https://i.imgur.com/JxEGRG8.png on Firefox. I'm typing this out on Internet Explorer, the only page that doesn't error on Firefox is my profile.
I do use add-ons such as NoScirpt but I have Sololearn white listed. How can I fix this?

Answer 1

The web version is... outdated to say the least. I recommend only the Android (not sure if iOS has caught up) app version. It has a ton more features, and will be a lot more stable.
But if you must use the web version, and the problem keeps happening, try... yuck... Chrome
Oh what am I saying? 🔥🦊 fur life!! Maybe email SoloLearn. Disable all your addons? Maybe even reinstall FF.