This is a resolution-related issue, usually occurring when changing phones.
To fix the problem, you need to:
– uninstall the app (to ensure no data is left in it)
– reinstall the app
– enter your login details
– press authenticate and, VERY IMPORTANT:
-> ensure you have a good internet connection.
-> do not switch to another app until the main scheduling screen opens.
-> do not let the screen turn off; if you see it starting to dim, tap it once.
-> if you are using an Android phone and it prompts you to stop the app or wait, choose to wait.