ADHD is complex. External factors that JaneWhite referenced indeed affect the efficacy of stimulant meds.
70% of those of us with ADHD respond well to stimulants. The 30% that do not respond to stimulants is not an insignificant number.
Stimulants produce euphoria when first taken. Many of us including self equate euphoria to a fix for our attention deficit. We felt depressed for years. We pop a ADHD pill and feel good. I have no bones about feeling good after years of feeling like hell. However the "feel good" does not eval to a decrease in the deficit we have in the attention/focus department.
I am keenly aware that the euphoria factor may not apply to you. I using the effect as an example of yet another of the many variables in play. More so I want to emphasize the 30% that do not respond to stimulant medications.
ADHD is not like autism where science has not yet come up with an effective fix. ADHD is relatively easy to control with medications and remedial psychological therapy. A "few good" psychiatrists are aware of the many non-stimulant meds and combinations that do work for the 30% stimulate med non-responders. As I write I find it necessary to control my anger that you and many others find it necessary to go out into cyber-science to seek relief when you should be able to call your PCP knowing that relief is just a few hundred bucks away.
Find a good psychiatrist.
Ask around. If you know anyone in the "inner circle" of the medical biz, ask them. I am proud to say my mother climbed the administrative ladder to second in command of a large NJ hospital. She had a saying. "I would not take Stover to [bozo doctor's name]." Stover was family dog - Fox Terrorier specifically - at the time. I hated that damn dog. When my wife and I visited I wanted Stover taken to [bozo doctor]. I could have loved a dead Stover.