- Edited
Hello machihkfyg and mitchellk
I had the same issue.
I share my solution 
The main plugging configuration:
Authority URL: * https://login.microsoftonline.com/common (multi tenant)
or
Authority URL: * https://login.microsoftonline.com/{Directory (tenant) ID} (Single tenant)
Authorization Endpoint: /oauth2/v2.0/authorize
And the bug with the url blank "api/auth/ext" with apache. The file .htaccess is fine, don't modify the file, the problem is the site location.
I modified the code inside the auth-openid-MS.phar.
The line with:
if ($_SERVER['SCRIPT_NAME'] === '/login.php' || $_SERVER['SCRIPT_NAME'] === '/open.php')
to
if (strpos($_SERVER['SCRIPT_NAME'],'/login.php') !== false || strpos($_SERVER['SCRIPT_NAME'],'/open.php') !== false)
Because, mi site work in domain.com/osTicket/, and the original condition don't match, and one Cookie param in never created.
And
The line with:
if ($_COOKIE['LOGIN_TYPE'] === 'CLIENT') header('Location: /login.php');
To
$url_home = rtrim($ost->getConfig()->getURL(), '/');
$sections = parse_url($url_home);
$sub_dir = isset($sections["path"])?$sections["path"]:"";
if ($_COOKIE['LOGIN_TYPE'] === 'CLIENT') header('Location: '.$sub_dir.'/login.php');Because my site work inside a sub-directory, and i need to get a good location.
I hope this could be useful for your!
My english is a work in progress
Best wishes
