The app has been down for a while as it's undergoing updates and maintenance recently.
Please delete the app and re-install it after 48 to 72 hours.
The in-home display needs to be re-binded, meaning you switch it off for 2 to 3 hours and after switching it back up you leave it as close as you can to the main electric meter and provide it 3 to 4 days to search meter network to connect.