Sync Issues with AAD Connect Service not updating attributes

Ok! I have it working again. I'll explain as best I can. After digging into some more details I discovered that basically every user was showing as failing in the Export to AAD step due to the error "ExceededAllowedLength".

When I dug into that, it was a Directory Extension attribute, "extension_[alphanumeric-string]_thumbnailphoto". We had tried to sync thumbnails to the cloud in the past, and I had been playing with it a couple of months back. I turned off all synching of directory extensions and any references to thumbnail attributes, but the errors remained there. I was all set to try uninstalling and reinstalling AADC on my backup server which was running in staging mode (where the errors had first started to appear) to try and clean out the local DB when a workmate remembered he had dealt with the same issue in the past, and opened a ticket with MS. They came back to him with a process to clear out the "Connector spaces" in AAD. Details below:

Open Synchronization Service manager tool as an administrator:

• Click on Connectors Tab
• Right click on the "Active Directory Domain Services" connector type and click Delete.
• In the 'Delete Connector' box, check 'Delete connector space Only' and click Ok > Yes > OK

Right click on 'Windows Azure Active Directory' connector and click Delete.

In the 'Delete Connector' box, check 'Delete connector space Only' and click Ok > Yes > OK

On the open PowerShell window, run the below command:

Start-AdSyncSyncCycle -PolicyType Initial

It's worth noting here that you need to disable the sync before you can delete the spaces using "Set-ADSyncScheduler -SyncCycleEnabled $false". Once you clean out the spaces, re-enable with the same command and "$true" (of course).

This fixed my issue, and cleaned up the logs heaps. And it's also worth noting that the issue above was stopping the sync of all sorts of changes (names, account details, org details, proxy addresses). Clearly, having that error in place stopped any other details from synching.

Thanks for helping out!