Magento 2 – Import Stuck “Please Wait” After SSL/HTTPS Configuration
2019, Jun 27
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://devdocs.magento.com/guides/v2.3/config-guide/secy/secy-xframe.html