401 error on Calendar

While loading Calendar, it shows the pop up box asking username and password… May be permission problem. Can anybody please help me to get rid from this…

Failed to load resource: the server responded with a status of 401 (Unauthorized) 

http://urlpath/vcal_server.php?type=vfb&source=outlook&noAuth=noAuth&user_id=7793f5bd-a35a-b165-c2b4-534d07ba8899

Hi there,

Please check your permissions are set to the required values for your OS/platform.

Thanks,

Will.

Hi Will,

I have set the required permissions for all the files and folder.
I have ProjectCRM folder and executed following command in the folder.
/www/ProjectCRM$ sudo chown www-data:www-data * -R
/www/ProjectCRM$ sudo chmod -R 755 .
/www/ProjectCRM$ sudo chmod -R 775 cache custom modules themes data upload config_override.php

You can see the screenshot.

We only get the login box while accessing Calendar. Please check 2nd screenshot.

By inspecting the element in browser this url is triggering that login box.
http://server.url/ProjectCRM/vcal_server.php?type=vfb&source=outlook&noAuth=noAuth&user_id=1

Please do reply