In my App i am using a Sharepoint List in Sharepoint Online.
In Preview mode in Designer Studio everything works fine, but if I run the App, data fields do not update changes done in Sharepoint, also Diagrams don´t work, some certain flields also show odd results, but back in Preview mode everything is fine.
I have had similar issues where it appeared to be working good in preview but not when I was launching an app from Dynamics 365. In the end it turned out to be that I was calling info from a list where no selection was made thus the no data or data updates. I had to change the calls to the correct list selection in order to work. For some reason the Preview mode used to work when it should not have. Maybe something similar is happening to you? More info of how your app is built and what it does would help to troubleshoot your problem.
i have a list in Sharpoint with a few rows for testing the App,
It´s the only data source connectet as showm in every tutorial.
Ist a simple App in Tablet Mode, Galery on the Left and Form on the right.
Sorry, English is not my mothertounge, so what do you want to know, and if i have the same problem like you, how kan i solve it?