Another scenarie maybe be when the target membership of main target is unselected, for example:
When i created the extension, by default the main target comes unselect, after turn selected works
julio_rennan
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I'm developing a live activity, and I had the same problem. I solved it by compiling the widget target before using it in the main target. You should try this in case the extension is unavailable in the main target. @hapiii @JeromeMF @philippnoah @turtlenerd