Ques : M2M authentication error – password invalid (code: 823)
This is the code that has popped up over and over again when I am signed up as admin trying to get to the home page.

Ans :  Access file“regenerate-platformhash.php” from browser which located under “/www/admin” directory of your adserver. When you access this file the new hash value will be generated and the error has been resolved.