URL's not working when initially activating ItemPress

I found this error myself when I wanted to add something to a site using ItemPress, and upon activation, I went to Items, added an Item, and tried to view it and got a 404.

This is natural of WordPress, as flush_rewrite_rules needs to be called. I tried coding in a solution today (https://bitbucket.org/aubreypwd/itempress-develop/commits/e239a04049a9ae3e62536d6377acaea58cd66d6a), but the standard way did not work.

So, I wrote in the flush via another hook and it’s called once, stores an option in the DB, and never does it again. This way is NOT desired, and I submitted to Hacks on WP.org: http://wordpress.org/support/topic/unable-to-use-register_activation_hook?replies=1#post-4954351 for help.

http://wordpress.org/plugins/itempress/