If you just planted them, they are likely growing roots first, then they will grow the foliage. If that is not the case, it may be your soil and the amount of sun they are getting. They actually like a poor soil and they prefer full sun. It can also take several years for the vine to get established.
I am in central Virginia, zone 7, and had trumpet vines with similar problems and mine hardly bloomed at all. I finally dug them up and planted passion flower vines. They have much prettier flowers and foliage, bloom all summer, are perennials and hummingbirds love them.
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