Today, PTC announced that CoCreate 17.0 is planned to be released in Q2.

ANSYS Workbench 12.1 supports CoCreate Modeling 2007 and 2008 (version 16). Version 16.5 should work as well.
Because version 17.0 has not been made available yet, support for CoCreate 17.0 with ANSYS Workbench 12.1 is not known at this time.