That's because names of the persistent attributes are case sensitive. In this case name of the persistent attribute is companies:

private Companies companies; 

but query tries to use Companies:

Join<Services, Companies> c = s.join("Companies", JoinType.INNER); 

That's because names of the persistent attributes are case sensitive. In this case name of the persistent attribute is companies:

private Companies companies; 

but query tries to use Companies:

Join<Services, Companies> c = s.join("Companies", JoinType.INNER); 

In join one should use companies as follows:

Join<Services, Companies> c = s.join("companies", JoinType.INNER);