The “To DeepL” add-on exhibits similar behavior; opening a new tab to send a translation request to DeepL may or may not receive a response. The official website itself may be unstable.
The pop-up translation feature functions normally.

El mejor hasta ahora por mientras no funcione por completo el del mismo navegador

Great! Big thanks to Filip! I just wrote a blog post about this extension. I'm thrilled :)

The most useful and easy to use addon for translation

Прекрасно работает в мобильной версии firefox beta

Getting the right info when you relocate can be vital. This add-ons saved my behind more than once. THX Filipe!

absolutely useful