This is the Firefox for Android feature where you click "Share", "Send to Other Devices" and the tab appears the next time you open Firefox on your laptop.
When the new Firefox Sync came out, it told me I would have to remove my account from the old Firefox Sync. I did so by following these instructions to unlink my devices and sign in. My bookmark sync is working fine, but sending from my phone Firefox to my desktop is broken. When I tap the little paper airplane to share to a device, it still pops up my computer name, and still says "Your tab was sent!" afterwards. But it never shows up as a new tab on my computer the way it did before.
Both my Firefoxes are up to date.