What's the sun exposure? What's the soil? It could be a number of things: trachelospermum likes it hot and sunny (I saw huge vines in bloom all over Italy, most in very sunny locations, and it needs regular watering and light fertilizer when it's young to get it established, and to maximize blooming.

Also, its roots could be struggling with thick clay soil or poor drainage, depending on where it's planted.

The rule with vines is the first year they sleep, the second they creep, the third year they leap -- it could be they're just taking time to establish roots and adjust to their location, and they'll take off this summer or next.

Hope this helps!

Jim