@m4iler @Mer__edith @signalapp “ The one difference I suspect may be at fault is the Privacy setting that "no one can see my phone number" in Profile - Privacy - Phone number “

Sounds like that is the difference yes. I’m assuming you have yours set at “Nobody” (which is the default) where as your friend has switched theirs to “Everybody” resulting in you getting their number but them not getting yours.

https://support.signal.org/hc/en-us/articles/6712070553754-Phone-Number-Privacy-and-Usernames#username_chat_initiate_other_side