I checked magento root directory and all other database, I couldn't find maintenance.flag file.
I have same error though
A 503 Service Unavailable Error is an HTTP response status code indicating that your web server operates properly, but it can't temporarily handle the request at the moment. This error happen for a wide variety of reasons. Normally, this error can be due to a temporary overloading or maintenance being performed on the server and it is resolved after a period of time or once another thread has been released by web-server application.
How to fix HTTP 503 errors
Reload (Refresh) the page
Restart Your Devices
Scan for Malware
Clear Temporary Files
Visiting the website later
Contact server admin
Could you please provide the path for maintenance. flag file.
How do you go about finding the "magento root directory"? I am having this issue as we speak and cannot access anything from the back end.
Delete this file on Magento root dir "maintenance.flag".
If you don't find maintenance.flag file on the root directory, then run this command on the Magento root directory.