Fiori Elements app Edit doesnt work

[#1]

I have a Fiori Elements application connected to SAP Business One (B1) through the Service Layer. The application loads data from a User-Defined Object (UDO) correctly. However, when I select a UDO record and click the Edit button, none of the fields become editable. All fields remain in read-only mode even though the app enters edit mode.

Below didnt work for me.
Checked if UDOs and OData are correct and are OK.
UI Facet anotaions are also OK (UI.FieldGroup | UI.LineItem)