iPhone could not be found

Same thing here. A few weeks ago I used Apple Pay via a website to order something from my iMac. As of yesterday things stopped working. I can't used Apple Pay for the original site when wanted to buy something else. I also tried it on Apple.com and got the same error message. I am not having any luck finding info online.

I contacted Apple Pay support and they were able to help me resolve the problem with some good old fashioned trouble shooting.

The only thing that seemed to work was booting in to safe mode so the system would blow out some caches related to Safari. Or that was the way I understood it.

We were able to come to that conclusion by creating a new user account on my iMac, setting up iCloud in said account and then using Safari from that account to trying to make a purchase form Apple.com and everything worked fine.

That was what seemed to work in my case. Your millage may vary.

I had the same issue and logging out iCloud and back in solved it.

Weird issue tho.

Thanks.

Exactly the same problem. Used to work but seems to have been killed with last Mojave update.

Thanks. However I managed to 'fix' it. Logged out of iCloud, Messages and FaceTime, restarted my iMac and logged back in. And Apple Pay was working again, as it had previously. Bloody nuisance.