"ERROR: General failure building project output groups" while creating Set Up project in Visual Studio 2019

I made a Windows Form App for borehole heat exchangers simulation, consisting only of one Form. When trying to build a set up project to install the app, I constantly get an error in the building. Message appears like below, and 4 times each message. All this is using Visual Studio 2019 updated.

    ERROR: General failure building project output groups
    ERROR: Unrecoverable build error - 0x80004005

I checked that every image used in the app are in the source file, that I have done the building in the right order, but every time I create a project output, no .xml file appears.

Although I think it should be not an issue, the program also created a Form1.resx file that sends a message (not an error, neither a warning) Object reference not set to an instance of an object. I don´t remember creating such thing. I tried to erase it and almost got my app deleted.

Does anybody now what can be the problem and how to fix it?

Mainly my process consisted in building classes that represent different modellings of a borehole heat exchanger. I then made the program build an "borehole" object of the certain class you choose in a ComboBox. I had no fundamentals whatsoever in coding so maybe this is not the way I should do that, maybe it shouldn't be classes. The app works perfectly on debugging mode.

Public Class Modelo2D
    Inherits ModeloNTU
 Public ReadOnly Property Calor2D As Double

Is there a problem in this?