Storage only works on Ionic Lab

I have an issue, wich I can not solve on my own (Trust me I tried). The problem I have is that I implemented the Storage in my project (I am working on Ionic 4 Basis) and everything works perfectly fine, when I use Ionic lab. But when I build the app and try to run it on my device (using xcode) or the simulator, nothing works as it should … So the storage is not working at all.

I hope some of you had the same issue and can help me solve my problem.

With best regards Lukas