Depends on what pruning group it is in. The vitacellas, with smaller but more numerous flowers, do not bloom until midseason, which for me is July. These are the ones you cut back to just above the third leaf bud when Forsythias bloom.

But more likely you have an ELF (early large flowered) one.
These are more easily available. They are not supposed to be cut back until the first flush of flowers are done, since the flowers come on new stems that grow from the old stems (aka old wood), not from the roots and through the ground. Then you can cut back the stems by 1/3 to 1/2 their height, and feed well. You will probably have a second batch of flowers in the Fall.

But not to worry, if you cut an elf like a hard prune type, which also incudes late large flowered ones like Jackmanii.
All this does is delay the flowering a bit. In fact, many experienced clem growers treat almost all new young clems as hard prune for the first Spring they come up in their gardens. This is suposed to help the plant grow stronger roots so it will put up more stems from the ground and make a bushier plant. Even if you have to sacrifice (or delay) the first flowers, you will have a better plant in the long run.
When I say "old wood" that does not mean that you have to wait a whole year for the stems to become old wood. They should reach this stage in a few months, especially if you feed them often with rose or tomato fertilizer, but not when they have buds or blooms.
Give your baby some time, buds may be forming as we speak.
If you have more questions, feel free to as us.

Marie in Maine

Agree with Marie. Give it some time. It is a year old clematis that you pruned back this year and may just be still settling in and developing enough old wood to bloom.

Thank you so much. I will have to be patient. How will I know how to prune next year? I bought it at Wal-Mart (gasp!) last spring. I remember on the tag that it is supposed to have large purple flowers. Other than that I don't know what kind it is. It hasn't ever bloomed.

Pruning the wrong way will only delay flowers, not hurt the plant. Pruning hard will help it get established no matter what Clematis it is.

Clematis are not instant gratification plants. They take several years to get established.

I agree with what BorS said. I would hard prune it next winter/early spring and it will be the better for it. Based on your description of it, I would bet it is a type II clematis.