Use clue 3 to get some more Xs.
You know that June 14 is Jeffrey. Replace the right side of the clue with Harry and Jeffrey. That will give you six more Xs.
Looking at the left side of clue 3, you know that the architect cannot be Canada. So you know that the left side of clue 3 can never include Canada. This implies that neither Harry nor June 14th can be Canada. This gives you 2 more Xs.
Now look at clue 6.
You know that June 14th is Jeffrey. So you know that the engineer is either Charles or Jeffrey. That gives you 3 more Xs.
Hope that helps!