Site will not refresh on other computers

Hi everyone, I have been working on my wordpress site for about 2 weeks now. I decided to change the home page slider picture and when I do it will not show up on my website when I access it through other computers. I have tried caching the computers but can not figure out the issue. My site is www.greekproud.org any help would be greatly appreciated!

Hello there,

I found your site is cached with W3 Total Cache plugin. You should have to flush it whenever apply some changes. Otherwise it’ll still load the older version of your site.

https://codex.wordpress.org/I_Make_Changes_and_Nothing_Happens

Regards,
Kharis