I added a cross sells product to the product and set it to display in the shopping cart,
but it is not actually displayed.
Please help check it, thank you!
May be there is an issue with the 3rd party plugins. Please deactivate all the 3rd party plugins and activate only theme-required plugins on the site and then check the issue. I am sure your issue will be solved. Then Activate the 3rd party plugins one by one and check which plugin is creating the issue for you.
Otherwise, if the issue still exists then keep the 3rd party plugins deactivated and let me know I will check and give you a possible solution.