Hi mr_psm,
Turning on the Desktop or other reminder methods there will enable those to be possible ways to get reminders. Then, you can set when you'd like to receive reminders in the Daily Digest and Reminders sections, and those will apply to the apps.

The desktop and Android reminders are a bit unique: both reminders are sent from the app on your device (computer, Android) so the app needs to be open—in the background is sufficient.

Also, the Android reminders need to be enabled in the Android app. They will use the timings from the web/desktop app but there's a setting to turn them on in the app.

If you have any further problems with either of those, can you contact us so we can help more specifically with either or both of those?