Hi,

Sorry for that. Here are several suggestions/questions:

• Try renaming your desktop device in Firefox Sync settings (Firefox Settings > Sync > Change Device Name...) to something unique and then send a tab to it. It might have happened that your device got kinda duplicated, and you are sending tabs to an old device version that in fact no longer exists.
• If you create a new Firefox profile (don't confuse it with a Mozilla account), sign in there, set another unique Sync device name and try sending tabs to it, won't that work?
• A question that seems unrelated, but... It could possibly be related. In Firefox Settings > Privacy & Security > (scroll down to) Permissions > Notifications, don't you have "Block new requests asking to allow notifications" checked?
• Just in case, please make sure you have notifications enabled on both devices (in general and for Firefox specifically).

Looking forward to your update!

Alright, so, I tried renaming the sync device but that didn't work.

Checked my settings and "Block new requests asking to allow notifications" is not checked.

Created a new profile and changed the sync name and that worked. Though I didn't attempt to send a tab before changing so idk if that would've worked or not.

Went back to the default profile and changed my sync name AND the sync name of my mobile device for the heck of it, synced/resynced and still won't send to that profile.

Just to note, I haven't changed any settings between this first happening and now. I've merely updated Firefox to whatever latest version it updates to each time.

So, (though I'm not really an expert here) looks like your main profile fails to get a valid endpoint for sending tabs for some reason... The only way I can suggest (with my limited knowledge and experience) is moving to the new profile that works. Please see the following articles on how to do that:

• Restore bookmarks, passwords and data from an old Firefox profile
• About your important data and their files

Regarding further steps, you can:

• Post a reply here so that the question remains on the radar of other contributors
• Create a bug on Bugzilla, Mozilla's bug tracker, so that your issue has a chance to be properly investigated (though I don't know whether the team has capacity for that)

Anyway, the steps above shouldn't block you from trying to move your files to the new profile. Hope that will work!