I can't speak for others but it took me until I had a heart attack to be diagnosed with chronic tachycardia. When my body has tachycardia episodes, I could be vomiting, dizzy, pain in my chest, it can trigger my asthma, just to name a few symptoms, and no doctor believed me that I was having these symptoms until it was formally diagnosed after my heart attack. Unfortunately medicak bias is real and many patients have genuine medical needs dismissed by the system. Not saying that's what's happening here, but it could be why doctors aren't providing a diagnosis.