Hello @steve1956, and welcome to the Parkinson's Support group on Mayo Clinic Connect. I can empathize with you. I had symptoms of PD for at least 10 years prior to my diagnosis and went to several different neurologists trying to find an answer. I finally found a neurologist who suspected PD and, after doing other diagnostic tests to rule out other neurological disorders, gave me a prescription for Carbidopa/Levodopa (C/L). I titrated C/L until I was up to three tablets a day. It made a tremendous difference in my symptoms, so it was determined that I had PD.

While this does sound like a rather unusual way to diagnose any disorder, it is not unheard of when it comes to PD.

My symptoms of PD were balance problems, an awkward gait (staggering at times), foot dragging, and right-sided weakness. In addition, I had a very soft voice. Are any of these symptoms familiar to you?

Here is some information from the Mayo Clinic website regarding PD and ways it can be diagnosed
https://www.mayoclinic.org/diseases-conditions/parkinsons-disease/diagnosis-treatment/drc-20376062
As you look at the diagnostic methods, you will see,

"A short, low-dose treatment of medicines. You may be given medicines used to treat Parkinson's disease to see if you get better. If your symptoms show significant improvement, this may help confirm your diagnosis. You must be given a sufficient dose to show the benefit, as getting low doses for a day or two isn't reliable."

After several years of taking C/L, I changed to a hospital system that provided the DAT Scan. The results of mine were normal, just like yours. I tried to go off of the C/L but was not able to as the symptoms increased.

I hope you keep searching for answers. Will you post again and let me know how you are doing with this process?