Hi there brucewyne,
The way the plugin is supposed to work within our plugin, is that in between the time set to cache (e.g. 10 minutes), and the next time the cache period (the 10 minutes) expires, it pulls a copy of the Instagram image/s from the local cache rather than Instagram, to speed up performance.
From your description, it appears that your site is not building a cache. It seems like it may be an issue between your installation of WordPress, and our caching function.
If this is the case, every time a user is loading the page, the page is waiting for new information directly from the Instagram servers.
If you're a technical user, you can do the following:
You can find out what the particular caching problem is by enabling the WordPress debug output, and it can be traced from there.
To activate the debug output, edit the wp-config.php file and change the line:
If you'd like us to take a look, please contact us through http://www.velomedia.com/contact/ with your site URL and temporary login credentials. For the open source community plugin support, we can't guarantee immediate turnaround from one of our engineers, but we will get someone on it as soon as possible.