File not found in enterprise

I have been creating a series of O-Rings and drawings for them. The parts and drawings check in and check out of our Enterprise vault with no problems.  When a user tried to put them into an assembly, they assemble OK, the drawing looks ok, Checks in ok.  Then a different  user tries to open the assembly the error message is "file not found in enterprise" or something like that. This is for the O-Ring only.   The assembly file does not show  the O-Ring in the list of parts to be checked out? 

Does anyone have any thoughts on this?

Is there a way to have a part that is in the vault,  in an assembly, but not recognised by Solidworks PDM?

Rick

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