can't locate foreign key

Hi,

Newbie question. if this is not the right forum, let me know (I'm sure someone will!) SQL SERVER 2012 - I cannot create a foreign key. Error is:

 Unable to create relationship 'FK_tblPersonnel_tblCompany'. 
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_tblPersonnel_tblCompany". The conflict occurred in database "WellService2_BE", table "dbo.tblCompany", column 'CompanyPK'.

 Problem is, I cannot find the constraint at all - see query output attached. Looked at every key, index, constraint - cannot find one with that name. CompanyPK is the primary key in tblCompany

Thank you -