imessage effects can be received but not sent
On my old iPhone 6 Plus I had a problem where I could send iMessage effects, but not receive them. I resolved this by disabling Reduced Motion and by signing into iMessage (somehow I'd been using my phone for ages while being signed out of that!).
Today my iPhone 7 Plus arrived and I now have the opposite problem - I can receive the effects but I can't send them. When I click and hold on the Blue arrow after a few seconds the screen goes blurry except for the text I've just written. I get no menu showing me the various effect options.
Any ideas what is causing this? I've tried toggling Reduced Motion on and off, iMessage on and off, signing out of iMessage and back in again but none of that has made a difference.
iPhone 7 Plus, iOS 10, null