Alexa is not talking to an app on your phone. It is dialling your number, the way any other caller would. So the call inherits every rule your phone applies to calls, and there are three of them that usually explain a silent phone.
The ringer is off. A muted phone does not ring for anyone, and no caller can override that from their side.
A Focus or Do Not Disturb is on. On iPhone, a Focus such as Do Not Disturb or Sleep silences calls except from the people you allowed under Settings > Focus > (your Focus) > People. On Android the same job is done by Modes or Do Not Disturb, where notification filters decide which calls get through.
The number is unknown. Your Echo dials from a number that is not in your contacts. On iPhone, Silence Unknown Callers sends anything unrecognised straight to voicemail, and that alone is enough to keep the phone quiet even with no Focus active.
You can force a way through: save the number your Echo calls from as a contact, allow that contact in your Focus or your Do Not Disturb settings, and call twice in a row. It works, and it has two costs. It breaks whenever Amazon changes the outbound number, and it means anyone who dials that number can wake you at three in the morning.
How RingIt helps
RingIt sidesteps the problem rather than working around it. The ring arrives as a push notification to the app, not as a phone call, so the silent switch and Do Not Disturb do not apply to it: on iOS it is a critical alert, on Android an alert channel that bypasses silent mode. Someone you invited by email taps once and the phone rings. It has to be set up before the phone goes missing, it needs the phone to be on and online, and it tells you nothing about where the phone is.
The full picture, including what Alexa can and cannot do here, is in the guide to finding your phone with Alexa.
