Unsolved problem with index.php and .htaccess files

Hello everybody, I am not very proficiente in coding so I am a bit lost here.

The issue is that I had a primary domain (habilidadsocial.com) working fine with a wordpress blog hosted in Hostgator. One week ago I created an addon domain (comprarunatablet.net) and it also worked fine, but when yesterday I tried to enter my primary domain’s dashboard I got the “Index of /” error with the list of folders of my primary domaing and also the notification “Apache server at habilidadsocial.com Port 80”.

I investigated and noticed it usually is a problem of the index.pho file. I stated on the cPanel file manager that my primary domain had no index.php file (¿?) so I created a new one. But it didn’t solve the issue.

I also wrote DirectoryIndex index.php at the beginning of my primary’s domain .htaccess file but nothing. I have no clue where the problem is. My subdomain has its own index.php and .htaccess files and works fine. It seems that when I installed the subdomain, some issue happened with my primary domain’s index.php or .htaccess files.

I don’t seem able to find a solution for the problem with my primary domaing. Any suggestion would be much appreciated.

Thanks in advance

Pau