This is because your Firefox version is not up to date (You must be v128+). You can either update Firefox, or install an older version of the Add-On (v2.13)

Also : updating your comment does not notify me. So next time, either open an issue on github or delete your old comment and add a new one. Thanks

Fixed in v2.8.3.
Edit: Thanks for updating your vote 🙏

As mentioned in the description, this add-on is DESKTOP ONLY.

Edit : The Add-On is now available on Firefox for Android since v2.18.0

v2.7.0 now support DeArrow,
But you need to change two settings in DeArrow :
- Enable "Only format user-submitted titles".
- Do not enable "Remove Emojis".

You will loose DeArrow format for non user-submitted titles, but it will let our Add-On keeping them in their original language.