Mine did the same thing, it was so hot I was unable to keep it moist enough. Many of my Clematis look particular bad this year.

I'd suspect insufficient watering as well. We had an unusually hot and dry summer and that's made it difficult for some plants to establish well, especially if located in that sunny a location. Clematis armandii is a very shade tolerant species - in fact, it is recommended for shade (considered a shade vine). I might consider cutting it back hard and relocating it to a more protected, shadier location. One that receives morning sun and afternoon shade is ideal. And keep it well watered until our fall rains kick in.

Can an overgrown Clematis armandii grow back from severe hard pruning & transplanting at the same time?

This plant is approximately 10 years old & stem is as thick as my wrist with peeling bark.

Our daughter & son-i-l bought a house & it was there already. Last year pruned after flowering, but it was still too large for the cedar arbor & messy for the path/yard as well as shaded the vegetable garden area in their small yard. They decided they wanted it gone, but I wanted to save it. It was in full bloom today & sad to cut it down because we couldn't save any leaved stems to get it off the trellis.

I have several good spots for it that is part shade with good soil & can mulch with compost. Usually watering is only needed during our July-early September dry season. We have the root ball kept moist newspaper & burlap in a barrel sized pot.

Would it be best to pot it up with potting soil or put it in the ground to nurture it back to life & encourage buds to sprout?

Starting another thread.