Answer: It sounds like you are doing all you can, with the possible exception of providing more sunshine ( a thought for next year). These vines are tropicals and seem to take a long time to come into bloom in our northern clime. Once they start, though, they keep on going into the fall. Full sun, keep them well watered to avoid stress, maybe try some "blossom booster" type fertilizer (any fertilizer with a high middle number, following the label instructions). Note too that they open at night and close up in the morning. The wait is worth it!
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