403 - Forbidden: Access is denied Error

I moved my website to a new server with almost the same hardware/software configuration.
Nop 4.2 / Windows Server Datacenter 2016 / SQL Enterprise 2017 / Plesk 18
I set FULL CONTROL permission to the whole website folder for the host IUSER

The project had been working without any issue in former sever, but since I moved it to the new server I occasionally give 403 - Forbidden: Access is denied Error and refreshing doesn't solve, while a user or admin get this error another users and admin can continue working without error ..



This error can raise in any url ... shop and admin panel

I tried clearing Cookies on browser, And It worked!  but couple hours later again the error raises.
our  domain set to   https://domain.com, when error raise I manually changed the URL to WWW.domain.com, it redirects to https://domain.com and come up!

But we are loosing customers because they don't do these tests that I do.

Any Idea about this issue? We are in a very bad situation, any help will be appreciated

Maybe related to this
https://www.nopcommerce.com/en/boards/topic/74204/admin-configuration-settings-403-forbidden-access-is-denied-general-and-catalog-settings-only#251092

Hi,

go to "Web Application Firewall" under domain.com
after click to "ModSecurity Log File"
after look log files and understand whats happen..

If you see a block related to your problem, write down the id number and allow it from mod security.