Thank you for your post. In this case, it looks like you are attempting to export from Revit 2017 to Navisworks 2015. In this case, by default Revit export in the current version (2017 to 2017). Once 2018 is released, Revit 2017 will be able to export to 2018 NWC. The issue is when going back in time. Currently the Revit model would need to be in the 2015 format Navisworks to open the 2015 NWC exported file. Alternatively, you could open this NWC in a 2017 Navisworks trial, save it down as an 2015 NWD version and then have this for sue within the 2015 Navisworks product. I hope this helps. Please let us know if there are any questions. Thank you.
Save earlier version of Navis:
https://knowledge.autodesk.com/support/navisworks-products/learn-explore/caas/CloudHelp/cloudhelp/20...
Michael Bussiere II
Support Specialist
Product Support
Autodesk, Inc.