The AmpliFi app is meant to be accessed when either connected to the local AmpliFi network or via remote access (if enabled).
Once connected, if the AmpliFi app says 'unable to locate device', tap the top left drop down menu and select 'start wizard' or 'switch AmpliFi'.
This is an example of what the screen should show.
From there select your AmpliFi router and enter the credentials if prompted.
If problems arise and the router is not visible or is showing offline go to help.amplifi.com for 24/7 chat and email support.