I have created my website using Wordpress, I have done some css changes in the website. While ensuring that the changes are getting reflected, I found out these changes can be seen when website got accessed using IP address but when I accessed the same website using domain name these changes are not getting reflected.
What could be the reason for this?
As the comments suggest, it's probably a cache. Try doing Ctrl+F5 on the site for a hard refresh of the browser cache. If you have a Wordpress caching plugin, try and see if you can disable/refresh it. The cache might be per-domain, which is why the IP address reflects the changes earlier.