First forget about zone. All zones are only temperature ranges. As far as being in the sun herbaceous peonies do like sun but where you are you must be more realistic. The sun at your elevation is stong. Most that comment here are living at 1500 or less.

Because you are high dessert do you mulch your peony to conserve moisture? You can use rocks for this. Does your peony look healthy with lots of stems? Did you incorporate humus or other soil in the area surrounding peony? Are you in clay or sandy soil? What cultivar is your peony? If it is a full double your air temps may become too hot and fry the flower buds before they can open. You may need to purchase a second peony that is not a full double, japanese, semi-double, or single. Where it is at does it receive lawn type fertilizer from runoff?

It would really help if you gave the nearest town in your message as you could be near Flagstaff where the growing time is too short for most peonies or Phoenix where heat comes early.

Thx for responding! Yes, I do mulch, no it doens't get runoff fertilizer fromt he lawn. It's in a separate bed next to a patio. Rich, nice soil. no clay, no sand. Healthy plant with a fair amount of stems. While we are similar to Flagstaff and our growing season is short, there are a ton of peonies that do quite well int he community. I just think it's in the wrong place. Sorry, I don't know what cultivar.