3CX Debian 8.8 + 3CX PBX 15.5 - Exchange contact sync not working

[SECOIT GmbH]

I'm struggling with Exchange Contact Sync.

First of all I created an Exchange impersonated user account as per manual.
According to this thread I used the "Office 365" button to contact my Exchange 2013.
And according to this thread basic authentication needs to be enabled to get rid of the http 401 errors which also worked. (@3cx team - please add this to the manuals)

And now: In the IIS logs on des Exchange CAS I see the PBX contacting the server, successful authentication to the /EWS directory and... that's it. Nothing else is happening.
Is there any place on the PBX where I can find sync log files so I can trace what the system is doing?

 

[Lev]

You should find your logfile in /var/lib/3cxpbx/Instance1/Data/Logs/3cxSystemService.log

 

[SECOIT GmbH]

Thank you, Lev!
I was aware of the 3cxSystemService.log but it didn't show anything related to sync. My PBX seemed to be ignoring the Exchange settings completely. So I contacted support and this seems to be an error that can happen in rare circumstances and they provided a workaround by renaming a .DLL file.