My site frequently got error database connections problem so i contact with hosting. They told me that as below:
Your database connection errors are caused by your user hitting the MySQL Max_Connection limit. This means something in your code such as a plugin or theme is not closing the connection properly. A normal MySQL connection takes a few milliseconds and there can be 15 at one time, but if the connection is not closed the account will hit the limit and display the error. You will need to try disabling plugins and changing the theme to track down the cause of the error.
Then i tried to re-name plugin + theme folder in order to stop Max_Connection error but it's still presits.
Then i tried to re-name again to default, now the site display "Stylesheet is missing." problem. I'm sure that the theme folder still exist at right location.
This is really the problem make me feel down since i can not access my site anymore. Could you try to access my ftp or database to find out what's happened? (i will provide the log-in details)