asaLundberg I tweeted Timo and received the following to try out…
"This sounds that the devices are connected to different iCloud accounts. Please double-check in the system settings. Also try to make a change to the journal on one of the devices and sync again"
Both devices were connected to the same icloud account, so it wasn't that. But I did add a new entry on my iPhone and then synced again, and it all worked this time.
Hope it works for you as well.