Philipe:
Thanks so much for your attention and responses to this issue. I wonder, is there is anything that I can ask/suggest to Zoho to adjust in their CardDav server settings that would allow me to Sync contacts (add/edit) using Cardbook?
Here is the example error snippet from the log again:
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2017.02.17 15:14:09:702 : tBox-Zoho-Online : debug mode : response code : (new Number(500))
2017.02.17 15:14:09:703 : tBox-Zoho-Online : Contact TestFirst 01CitronTest2 failed to be updated on server (url : https://contacts.zoho.com/carddav/<mailbox>/default/contacts/729281fc-36aa-4ae9-9f72-2ec945ffdf58.vcf, status : 500)
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I can sync the original contacts FROM Zoho, so I know that I am logged in and connecting; however, I can not add or edit contacts from Cardbook, and get the above error.
Thanks again,
Todd