Must I have a paid Apple-Developer license to have my App work flawlessly on a Device vs only on Simulator?

I was nearly finished with my SwiftUI/Combine application and everything was working correctly via simulation.

However, upon using a device, I noticed the presented Views don't display within their own ZStack Layer when running on any device.

That is, I get a blank white screen when running the code on a device. Why the difference with the same code?

Is this a Screen-Builder flaw (code is large) and if so, why only on a device but not via simulator?

I don't have an active (purchased) developer membership.