Facebook Pixel and some other addons are greyed out

I’m trying to install Facebook Pixel addon, it’s greyed out but Install button works.
When I press it, nothing happens. In network logs I see access denied. Do I need to changed some permission to addon folder? Thanks

What version are you using? It may be a limitation of the free version.

No, it’s not a free version. It’s CS-Cartv4.17.2.SP2
I have license # pasted and it shows - Licensed product: CS-Cart

This could be caused by the ModSecurity Apache module.
https://docs.cs-cart.com/latest/install/possible_issues/forbidden_not_acceptable_errors.html

We recommend that you disable it, but also provide a configuration for it to work properly if it cannot be disabled:

mod_security should be disabled; if you don’t want to disable it fully, configure it to work with CS-Cart as described in this file;

The CS-Cart is installed on a server with Plesk. I have disabled ModSecurity, I’m still not able to install Facebook Pixel add-on. Any other suggestions? Thanks