When you say you “enabled Bonjour” on both devices, since you have it working you must have done it correctly, but for others reading this thread, only one device on the network should have Bonjour turned “on”. For me:
- iMac with macOS I consider the “server” and I have “accept incoming connections” turn on as “available” in the Sync Setting panel, and “off” on MacBook
- iPhone and iPad with iOS in “Settings”, Bonjour is turned “Off”
And yes (glad you found it), on iOS you have to turn the switch “on” for Bonjour in the Locations screen, and turn on/off your selection of databases to sync.
All this in the DEVONthink Manual.