'Authorization Failed' toast message at startup Every time I reboot my HTC One M8 Google Play Edition running 6.0 Marshmallow, there is a toast message that reads 'Authorization Failed' with no other information on what actually failed.

Any idea what is causing this so I can fix it?
Improvising Firelord's comment, if you are using  Linux, execute in terminal 

adb shell dumpsys window &gt; log.txt


and then, 

cat log.txt | grep 'TOAST'


Now, you can find the package name and app causing the problem.