Plugin works but blocks admin from viewing site

Hi this plugin definitely works in that it show the maintenance page, but I’m logged in as admin (obviously as i activated the plugin) and thats all i can see. I can understand whats preventing me from seeing my site – I also tried a couple of similar alternative plugins and I seem to run into the same issue, so i don’t think its the plugin – anyone have an idea of whats actually going on, thanks

Dan