Send Tab not working

I'm signed into Firefox on 4 devices. I can send tabs between all of them except from my work computer to my phone (other direction works). I can see the tabs open on my computer from my phone and tap to open it on my phone, but if I "send tab" from computer to phone, it never arrives.

I tried signing out on my phone and back in. Didn't work.

What else can I do to troubleshoot?