If the following error message is shown when trying to log into the Peatix app (iPhone) with a Twitter account: "Twitter returned an error so this app cannot continue to log you in to Peatix. Please review the settings of your Twitter account.", please follow the following steps to login:
1) Access the "Settings" of your iPhone
2) Select Twitter
3) Tap your user name (@xxxxxxxx) and click "Delete Account"
4) Re-enter user name & password and click "Sign in"
5) After you are signed in again, open the Peatix app and login with your Twitter account