I was also having the same issue with my blog (which I remind you I don’t touch that much), which I didn’t resolve by changing username and password on my configuration file, but I got it working by changing my hosting account password as well to try and force the system to fix the permissions! If it doesn’t work on your end try it as well:
Though the wait isn’t necessary, it’s still good measure to make sure your WordPress websites will work again. Also, make sure to update all your wp-config.php files to use the hosting account username and the newly-generated passwords instead of the ones Softaculous generated before everything will work on your end.