Experiencing same behaviour her. The app leaves to a browser and actually never comes back. There is a documentation hole on that point. I do not ever know where to search those config.xml or config.json mentionned in the track.
Doc says :
"When using the "Via a browser window" option, you can optionally specify
an URL scheme to be used by the system to open the Mobile app. By
default, the URL scheme used to open the app will be the one indicated
by the own app during the SSO process. If you've developed a custom app
using its own URL scheme and you want to allow only SSO logins via your
app, you can indicate there an URL scheme. The site will detect that
setting and will use it instead of the value indicated by the app."
Which sound a bit opaque to me. I am using the standard Moodle Mobile app so i'm just assuming that i would not have to care to that URL, but maybe i'm wrong. In that case, the definition of this url is a bit esoteric : "the one indicated
by the own app during the SSO process" ? hum.... i do not see even what it points to...