I have similar issue. Firstly when I build app my widgets doesn't list in widget. and I build extension and it adds widget to screen but it only black. I checked Console.app get these errors. one is shown in image other one Task [211] [com.emsal.ulakbelmobil::com.emsal.ulakbelmobil.SecondReporstsWidget:CrmExpiredActivityWidget] Encountered missing entry

Thanks for answer. I will look at it.