Packages ignored when opening folder

Symptom: You opened a folder which is not a Visual Studio Code project folder, i.e. a folder with no app.json file directly in the folder, and the module is not listed in the Solution page.

The cause is likely that the package is a runtime package. To verify this, check the Discovery page:

Prism for AL cannot load runtime packages as they are encrypted, so the only remedy for this issue is to use a normal (not runtime) package, if possible.