Log in to your hosting control panel ISPmanager.
Select menu «WWW - WWW-log files»
This menu contains the log files of all sites.
***.access.log - site access log
***error.log - website error log
To open the log file - click on it 2 times (or select the one you need and click the «View» button)
With the help of logs, you can determine the list of all requests to individual files or solve errors on the site, find out what exactly caused it.