The notification that you must "log in" is not for Facebook - you're already logged into Facebook. The login request is actually coming from the Facebook app used to create your deal, called Smart Deals. You must connect with this app in order to access the coupon or offer.
By connecting with the app, you are simply allowing us access to your basic Facebook information so that we can create a custom coupon voucher tailored specifically for you. This helps us assign coupons to each user, protecting businesses from coupon fraud.
How To Access A Deal With Facebook
When you see this pop-up on your screen, clicking the Go To App button is what allows you to print a coupon. If you click close you will not be able to access any deals. This allows the app to see your information and create a coupon for you.
Also, if the deal requires sharing or if you are trying to share a deal with a friend, you will have to allow the app to post on your behalf by clicking the Allow button. If you click skip, you will not be able to access any deals. This allows the app to send a post or message from your profile (you will have full control over what that message says and where it goes.)
In case you already clicked Close or Skip, reload the page and start over so you can access the deal again. You'll be asked you to accept both permissions once again, so you can accept them and get your deal!