Problem:

After I configured Let’s Encrypt on a CentOS server. I then configured my Magento 2 installation to use HTTPS on the admin side. Following these changes I could not import CSV files into Magento. The import process would just hang at “Please Wait” while doing a data check on the import file.

I opened the developer tool in Chrome and the console was showing this error:

in a frame because it set multiple 'X-Frame-Options' headers with conflicting values ('deny, deny, SAMEORIGIN'). Falling back to 'deny'.

In order to solve this I need to configure apache to allow X-Frame-Options on SAMEORIGIN.

Solution:

Edit This File:

/etc/httpd/conf.d/ss.conf

Change

X-Frame-Options DENY

To

X-Frame-Options SAMEORIGIN

Now restart Apache

sudo systemctl restart htpd

References:

https://magento.stackexchange.com/questions/189977/x-frame-options-headers-with-conflicting-values-when-tried-to-import-products

https://devdocs.magento.com/guides/v2.3/config-guide/secy/secy-xframe.html