How was her root system when she arrived and you planted her? Did it look strong and healthy?

@eri54, the root looked fine to me.

If the roots were in good shape and you planted it a bit deeper in the soil than it was in the pot, it should be OK. Most reputable sellers stop shopping about now because in summer, plants may cook in shipping and delivery vehicles. So your plant may have gotten a bit too hot. Keep it from drying out or being too soggy; a good layer of an organic mulch like shredded bark or compost or shredded leaves around the plant’s crown but not burying it will likely help keep the moisture even.

I would expect it to start sending shoots up in the next month, but if it doesn’t be patient and give it at least a year. Sometimes clematis reappear after a surprising a,punt of time.

What Babs said. Sounds like she's just lost leaves probably because she was stressed out during the transportation, but if the roots were healthy she will most likely come back -- if not this year. I think I read some posters here sharing their experiences of clems that disappeared (so presumably dead) but came back some years later to their surprise, even.