As the incoming connections seem indeed to be disabled on the iPad, the sync location on the Mac is not necessary anymore. Therefore it’s marked as offline as the iPad doesn’t work as a server.
Does restarting DEVONthink on the Mac or rebooting the Mac make a difference?
Wait, hold on… The iPad isn’t the server… The mac is! See my comment above “On MacOS DT3 (the server)”
And what sync location on the mac are you referring to?!
And no rebooting doesn’t make a difference.
The one selected on your screenshot.
Which screenshot?
Why did you refer to the iPad as the server when I’d said it was not?
The iCloud sync store is for my iPhone. But that doesn’t matter because I’m not asking about sync stores. I’m asking why is the direct connection between mac (server) and iPad failing? “offline”?
According to this screenshot and the obsolete mobile@ipad-5 sync location it seemed that the iPad is (still) a server too.
going to delete app and start again 
!
I have been having the same issues. Did deleting DT to Go help?
I’m not at all sure what your problem is. The thread is quite old. The Original Poster reported a problem with iCloud. If that is your problem, then be aware that for some people (many reports here) Apple’s iCloud and CloudKit syncing is unreliable. If you really need syncing then best to chose another method as there is no known way to reliably overcome Apple’s unreliability for those who experience it. And, un-install and re-install is probably not a good first step as it rarely fixes issues.
After looking at your “Log” to find symptoms, see “Sync Issues” section on page 185 of the outstanding DEVONthink Manual. Better first steps documented there.
I recommend you also consider changing to another synch method, start with Bonjour on your local network. It’s the fastest and most reliable. See the DEVONthink Handbook for specific instructions for how to set it up. And if you need third party external synching across the Internet, try the other methods in addition to Bonjour. You can keep your Apple iCloud/CloudKit sync if you want and hope it restarts sometime, I guess.
If you need additional help here, probably best to start a new thread and fully explain the issue, what you’ve done, how you have set it up, what problems you see, etc.
Well, the basic problem was that iCloud (legacy) was unreliable and and I couldn’t get Bonjour sync to work at all. Because I was trying to sync a very large data base I ran into storage problems and iPad stopped the sync. On another occasion my internet stopped and DT to go registered this as a timing -out. These effectively kept DT to Go from syncing. When I tried to reset Bonjour I ran into similar problems to those described in the thread I joined.
I had about 5000 synced items, but there was no reason for me to have most of them on my iPad. I was setting up a new, small database for of items I need on my iPad when traveling.
The simplest solution in my case was to delete DT to Go and start anew. Then I set up only Bonjour and only to sync my new small database.
Now everything works great and suits my needs and purposes perfectly.
Thanks for your response.
I was setting up a new, small database for of items I need on my iPad when traveling.
Excellent! We are big advocates of this approach to mobile data. Just like your wallet (or purse), it’s a good idea to carry what you may actually need instead of trying to carry everything you have.
Meh… I’ve got a ton of storage on my phone. I sync everything.
That’s your prerogative.
It’s descriptive, not prescriptive as we have a wide variety of users with a varying array of equipment. Not everyone has a 2TB iPad Pro.
Nor do I. But I do have 512GB iPhone, with more than enough room for 10GB of DEVONthink data. For me, in my particular setup and use case, syncing everything down to my phone works well and is extremely useful. Honestly, it’s one of the main reasons I use DEVONthink.
That’s excellent and we’re glad to hear it. 
My understanding was that Bonjour syncs would not work if a vpn was running. But the other day I had my vpn on and did a DTTG to DT3 sync and it worked! I think the vpn was only running on my iPad and not my MacBook at the time — would that have made a difference?
This is just a matter of curiosity on my part. Does anyone know if Bonjour syncs now normally work when a vpn’s are running?
Afaik, both devices have to be on the same network. If that’s a VPN or not might not be relevant as long as the network and network mask are the same.
What VPN are you using?
