Elaboration Errors in Harness
Typically, this error is caused by elaboration processing referencing another unit that has not been elaborated yet. In GNAT, there is a binder option that allows you to force elaboration processing to take place in the most "pessimistic" order, which usually resolves these issues.
You need to add the option "-p" to the binder options in the options dialog (Ada tab), and then recompile your environment. This should resolve your problem.