Ask Mr. Smarty Plants

The first thing that comes to mind is transplant shock, since you only planted it a month ago. This is something people overlook, as they buy a fresh, blooming plant, stick it in the dirt, and it suddenly droops. The most important thing: is there good drainage in that redwood planter? In other words, when you water, does water come out through drainage holes? Nothing will wipe a plant out sooner than standing in water. Once you've examined the drainage, here are some things to consider. The Star Jasmine, which is a native of China, needs a year or two to get a good root system going. Also, it blooms in April and May, ordinarily, and should bloom only sporadically the rest of the year. It is fully hardy in USDA Hardiness Zone 8, in a sunny location. The best we can tell, Contra Costa County, in the north central coastal area of California, is Zone 8, so it should be fine. Now, to deal with the transplant shock. Prune off the upper 1/2 to 1/3 of the plant, and trim out any crowded vines that are not looking well. This will give the as-yet undeveloped roots a little breather, with less upper growth to get water and nutrition to. Then, use a slow drip to water, sticking a hose in the planter, and just let it dribble (watching the drainage) until it seems all the soil is moist. You need to check the soil, and repeat this fairly frequently. Planters will dry out faster than plants in the ground, because they are exposed on all sides but the bottom to the air. Removing those leaves from the upper part of the plant will also help in preventing moisture loss by transpiration. Early next Spring, before blooming time, give it some fertilizer with a good proportion of phosphorus in it, to encourage blooming. And be patient!

This University of Florida Cooperative Extension website Trachelospermum jasminoides will give you more information.