This error is shown when you try to "Connect to an existing Monument".
It will occur when you had previously completed setup, changed your router/Wi-Fi connection and then uninstalled and reinstalled the app.
How To Fix
- Connect Monument to your new router with an Ethernet cable.
- Open the Monument App.
- Select "Connect to an Existing Monument".
- Complete setup.
- Go to Settings --> Change Wi-Fi Configuration.
- Select your 2.4GHz Wi-Fi connection point.
- Remove Ethernet cable (if you prefer Wi-Fi).