An example of a url hosted on DO servers
I have tested this URL and others everywhere else I can think of and not seeing the error.
These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.
It is difficult to determine the underlying issue when you are not able to replicate the issue. Since Facebook is reporting that it is receiving a 503 when reaching your page I would recommend taking a look at your web server’s log files. If your server returned a 503 error to the Facebook service it would be recorded in your log.
If you are running Apache:
On Ubuntu/Debian
/var/log/apache2/error.log
On CentOS/Fedora
/var/log/httpd/error.log
If you are running Nginx:
/var/log/nginx/error.log
All errors your server returns are recorded here by default usually with additional information about the error encountered.