Thank you for contacting the UVM Master Gardener Helpline with your question about your peony. How frustrating that what looks like a very healthy plant is taking a year off. It is interesting that it is just a single plant.

Has this peony received any different treatment than the others? Is it in a different location than the others?

I consulted with the experts on the UVM Helpline and they responded “This doesn't appear to look like typical disease issues we see with peony so it may be an abiotic issue, i.e. it could be related the weather, soil nutrients, and/or sunlight deficiency. "

Ann Hazelrigg, the director of the Plant Diagnostic Clinic, followed up with “The plant looks great. I suspect the little buds were produced during the very rainy weather and they may have died due to internal rot ie the plant just missed the window of opportunity due to weather at a critical point in bud development. You may just have to give it a pass this season, but it looks healthy otherwise so i would not suspect any root issue lower in the plant. “

I found this article that directly speaks to your question: “Reasons why Peonies Fail to Bloom” published by the Iowa State University Extension: https://yardandgarden.extension.iastate.edu/how-to/reasons-why-peonies-fail-bloom. Most of the suggestions do not appear to apply, unless you fertilized that plant more than the others, it needs dividing, or has developed a fungal disease.

Another article suggests impact from a late frost; “Flower buds form on my peonies, but don’t open. Why?” also from Iowa Extension: https://yardandgarden.extension.iastate.edu/faq/flower-buds-form-my-peonies-dont-open-why .

The final article I offer is also from Iowa State University Extension and provides general information about issues with peonies: https://yardandgarden.extension.iastate.edu/how-to/how-manage-potential-problems-growing-peonies.

I’m giving you all the articles I found in case you see something that I am missing.

I hope this information is helpful. If you have any additional questions, please feel free to reach out.  Good luck with your peonies!