For the next release we are working on the following new features:
--Configurable cache directory, to help with some server configurations where directories inside wp-content/plugins are not writable.
--Separate error messages for separate cases of "cannot create folder/nonexistent folder" and "cannot write to folder".
--Link to the plugin settings page on the installed plugins page.
In the meantime, for anyone having issues with the creation of the "cache" folder inside wp-content/plugins/easy-instagram, if you have the proper access please try adjusting the folder permissions.