Sun Parasol® is vigorous, so it’s likely to be pot-bound and to lack of fertilizer. They causes lower leaf to turn yellow or not to flower. So it’s recommended to transplant the plants into larger pot, right after purchasing them. Then they will generally flower until the day length gets below 12 hours, so for several months. When transplanting, remove old support truss, and wrap the vine around a new support truss or trellis.
Keep in mind there is no guarantee that this information will always work, climatic conditions will have an effect in any environment. Again, this information and the related advices of this web site are solely based on past experience and expertise and no other, and in no case shall be constructed to provide a guarantee that certain particular purpose or results will be achieved.