I am pretty sure you have already heard about this issue. It usually happens when you try to update WP, a theme or a plugin and something didn’t go well. Since there has been a problem, WP will automatically display this page error.
It’s really easy to solve though. You go to your root domain using a FTP software and then you will see a .maintenance file that you need to delete. And then the magic happens, your site is back on.
But what happens when the .maintenance does not exist and your website is working except for the main page?
Well trust me, it took me 2 hours to figure that out.
When googling the issue I was only getting the ‘delete the .maintenance’ solution. Of course that is not helping since, hell, there is NO .maintenance file anywhere. People asked me to look for hidden files which I did but since I was able to see my .htaccess the problem was obviously different.
Some people are also advising to delete the upgrade folder on your wp-content folder. But guess what, again, not working.
Since I had access to my back end (wp-admin) I disabled every plugins but no luck.
I was about to give up when I decided to delete my .htaccess and there it was! I got a message telling me that I was obviously using PHP 4.4.9 and I needed to upgrade to 5.2.4. But that didn’t make any sense since I am using PHP 5.
Anyway I transferred the exact same .htaccess back into my server and tadaaa everything was working again! I am not sure how. I have contacted my host to see where the problem lies.
Anyway if you are having the exact same problem, try to solve it by deleting your .htaccess! Might resolve the main page issue.