Is it normal for adhd meds to suddenly stop working?

I recently started taking meds for my ADHD and it’s helped tremendously, for the first few days I felt like I could actually function again. Sadly though, after about a week, maybe even less, they suddenly and without any warning, just stopped working entirely. Like I could pop 2 and go take a nap without any problem. For reference, I’m on brand name adderall Xr 20mg.