How can the program be prevented from running in the background?

[Alpacala]

I made additions to my program that I prepared using Visual Studio WinForms.

I am also keeping the previous version separately.

When I start the previous version with F5, I can preview it.

However, when I press F5 for the new version, unfortunately, the program does not enter preview mode.

When I try to open the EXE file created in the bin and obj folders, I get an error due to it running in the background.

Even though I close the program that appears in the Task Manager, I still cannot perform the installation.

No error appears on the screen.

The error only occurs in the designer section of one of the forms.

It says: this.SuspendLayout(false);

What is my issue and how can I solve it? I am an amateur with moderate skills but lacking in details.

Regards...