Which addon are you trying to install? Not all addons that are created for desktop Firefox work with Firefox for Android. It is likely that this one is incompatible.

This is probably about sorting bookmarks with an extension like Bookmark Organizer.

• /questions/1261877 What addon helps sort mobile bookmarks?

(I've locked that question to keep the discussion in this tread)

I use a Note 8. I've tried Bookmark Organizer and others, all available at Firefox Addons, but can't get any to work. I simply want to sort my Firefox bookmarks with my cell. Please advise. Thanks.

You have asked about sorting bookmarks before and got the answer that this feature is currently not supported. I think that this still holds.

• /questions/1227018 Sorting bookmark folders in Android

I'd like to use Bookmark Manager or any of the other bookmark related extensions affiliated with Firecox addons. Are any made to work with a mobile device? A Samsung Note 8?

There aren't that many bookmark extensions for Android:

• https://addons.mozilla.org/en-US/android/
• https://addons.mozilla.org/en-US/android/collections/4757633/bookmark-managers/