Why is “Allow from this source” grayed out?

If “Allow from this source” is grayed out, our app is not blocking the installation — a higher-level Android or admin policy is. Since Android 8, permission to install from unknown sources has been tied to the specific source app. Device manufacturers may also restrict this choice in individual cases. In work profiles or on managed devices, companies can additionally block installations from unknown sources — according to Android Enterprise, in certain constellations even by default.

If that is the case for you, one of these paths usually helps:

• use the Google Play version,
• have the blocking policy adjusted by your IT administrator,
• or use a different, unmanaged device.