I have been trying to figure this out for 3 days and to no avail! I read the instructions on how to put Magento into maintenance mode by inserting the maintenance.flag file into the root of my public html file folder, but it is not working. Also, the instructions state code that I will need to find/insert/modify around lines 47-48 and line 59 inside my index.php file, but the new 2.1.6 version only stops at line 39 in the index.php file! I also tried to find a feature in my Admin panel to see if maybe there is a feature where I can select to turn the maintenance mode on, and I could not find this feature in the Admin panel. So I am assuming that the instructions to put the Magento into maintenance mode is only for the OLDER versions and may not be for the 2.1.6 version??? I prefer not to downgrade my version to get this to work, but any advice would be appreciated! Thanks!!!
I was doing all that stuff man this is crazy took me ages but look this is what you need:
ENABLE SSH so you can use the command line!!
magento 2 is supouse to run everything from that CLI.
Install winSCP in your PC, connetc to your SFTP connect do the whole steps until you can use te CL. after that guess what all you need to do toenable maintenance is type:
php bin/magento maintenance:enable
here is a list of all the commands
Accept this as solved!