If you are having problems with the Outlook App on your Android Phone there are some steps you take.

Go to the Google Play store and make sure you have the latest version of the Outlook app installed.  The easiest way is to search for outlook and if it just says open then it is up to date.  If the button says update, press it to update the app. 

Go to the phone settings then apps.  Touch Outlook and then storage and cache.  Touch clear cache.

If the issue continues removing and re-adding the account would be the next option.   Go into the Outlook app and touch the icon in the top left-hand corner and then touch the sprocket at the very bottom.  Touch your account and go to the bottom and the page and touch delete account.  Go back through the same steps to get into the settings and touch add your account and add your account back to the device. 

If that doesn’t resolve, you’ll want to go to the phone settings then apps.  Scroll till you see Outlook and touch to open.  Touch storage and cache.  Touch clear cache and the touch clear storage.  This will remove all settings from Outlook so that when you re-install it is a fresh install.  Some say you don’t need to do this step but I always do be sure there is nothing lingering.   Go back to the first setting screen for Outlook and choose uninstall.   After it is uninstalled go to the play store and search for Outlook.  Download and install again.   Open the app and re-add your accounts.