Diagnosis
The dishwasher isn't successfully joining your home Wi-Fi network. The blinking red light on the door is the Wi-Fi indicator telling you it's in setup mode but failing to connect. This is almost always a network compatibility or password issue.
How to Fix It
First, you need to use the Miele app to add the appliance. Make sure your phone is on the 2.4 GHz band of your Wi-Fi—Miele appliances don't connect to 5 GHz networks. During setup, when the app asks for your Wi-Fi password, type it in manually; don't use a saved or auto-filled one, as hidden characters can mess it up. Keep your phone close to the dishwasher during the whole process.
If That Didn't Work
Try a full reset of the dishwasher's network module. Press and hold the "OK" and "Start" buttons on the control panel simultaneously for about 5 seconds until you hear a beep. The Wi-Fi light should go off. Then power cycle the dishwasher by turning it off at the circuit breaker for a full minute, turn it back on, and start the app setup process from scratch.
Heads Up
The AutoDos detergent system setup is a separate step in the app and won't work correctly until the basic Wi-Fi connection is solid. Don't skip it.