Answer: Clematis are not all-season bloomers. (For closer to all season bloom you would use an annual vine.) Most clematis bloom in the spring or early summer and may bloom again later in the season if conditions are good. There is also the sweet autumn clematis which blooms once a year but in the fall. So it may be that your plant has already bloomed for the year, or not yet.
I am a little concerned about trying to keep it all winter as a container plant. The problem is that the roots are not as well insulated as they would be in the ground so they are subject to not only extreme cold but also more temperature fluctuations which are extremely stressful. You might try moving it to a sheltered location out of the wind and heaping mulch over the container (do not allow it to touch the plant itself) or possibly move it to a friend's garage where it can be stored cold and dark -- but not quite freezing. If you do this, keep the soil barely moist, water just enough that it does not go bone dry.
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