If you run Wordpress on HTTP-only host or instance which is behind HTTPS proxy it is highly possible you will get infinite redirect loop to HTTPS.

To fix that you need to modify the file wp-config.php and add following lines:

if($_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https'){

$_SERVER['HTTPS'] = 'on';

$_SERVER['SERVER_PORT'] = 443; }