When reinstalling the app you will need to make sure your device doesn't save your previous data. If your backup is turned on, your device will restore your previous data and reinstalling will not solve the issue.
Here are the steps to turn your auto backup off and reinstall the app:
1. Close the app completely by going to recent apps and sliding the app closed
2. Go to System Preferences > Settings > Backup (& Restore) and turn it off. It may be labeled differently or located somewhere else in the system preferences depending on Android version and phone manufacturer
3. Completely delete the app from your phone by long pressing the app icon in your app drawer and either clicking uninstall or dragging to top to uninstall
4. Go to Google Play and re-install the app
5. When the app opens, it should start at the welcome screen where you can either sign up or login. IF you are already logged in, then the backup was restored and you didn’t turn backup and restore functionality off correctly in step 2
6. Log in with your credentials.