The only supported cache plugin is Redis Object Cache which is installed and activated by default. Do not install other cache plugins.
Click Flush Cache in WordPress navbar on top.
If you can't access the dashboard, you can go to WP-CLI and click Restart PHP Workers.
Image/CSS CDN Cache
If you changed images or your CSS is not refreshing with regular Flush Cache, you need to Flush CDN Cache as well. Go to Addons > KeyCDN and click the link.