I wanted to use zetadocs on NAV 2013 R2. I already had a NAV 2015 zetadocs installation.
On 2013 I was getting this error even though I had a Zetadocs Archive (not sharepoint)
Turns out, if the zetadocs folder is from a newer zetadocs (v7.xx) and the fobs I had in the db was from an older installation (6.xx) it would give this error.
solution: replace the objects with 7.xx version
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