There are two types of stimulants: amphetamine (Adderall, Vyvanse, Evekeo…) and methylphenidate (Ritalin, Concerta, Quillivant…). Almost everyone does well on one type or the other, but not both. And Dex is really a category of it’s own, even though it’s not categorized separately. This means you likely need to try a different type of stimulant medication.
Here’s more detail on how medication works and how to get the right med and dosage:
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism