The Google Wifi app will no longer be supported and will be removed from Google Play in June.

We’re moving the control of OnHub and Google Wifi devices to the Google Home app. You can easily migrate your Google Wifi network into the Google Home app where you’ll be able to control your Wi-Fi network and other connected products in one place.

When you migrate you’ll get features like:
Improved video conferencing on Google Meet and Zoom.
Better insights on your network whether it’s a notification when a new device joins your network or detailed insights for troubleshooting a bad internet connection.
More ways to control your Wi-Fi. Use Google Assistant to pause Wi-Fi or check your internet speed hands-free.

After the Google Wifi app is removed you’ll need to use the Google Home app to add new devices or to modify expand or create networks.