Answer: This is an extremely versatile vine and can grow nearly anywhere, your site sounds fine with the only exception being if it is exceptionally wet.
It is not unusual for a new vine to take a couple of years to settle in and really take off at its full normal speed, but FOUR years! By now I would have expected it to have engulfed your trellis and begun climbing the roof.
I would wonder if there is an obstruction underground (eg patio footing just below the depth you dug to plant) or if for some reason the roots are constricted (large rock underground); if maybe at some time in the past something unusual happened to the soil in that spot; if somehow maybe the roots have not spread beyond the original planting hole (rootbound at planting or sheer sided clay hole); if a vole has been dining on the roots, or long term herbicide was used there long ago, or there is a gas leak nearby or .... there must be some limiting factor.
At this point since you basically have nothing to lose, I would suggest digging it up to check the roots. If they are encircling and strangling the plant you can trim them back and reset the plant, make sure to loosen the soil over a wide area to encourage wider rooting. Other than that, I am stumped. I'm sorry you are having trouble with it.
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