It says I've already enterd today, when I haven't. Just shows a page of prizes which says which ones I am supposed to have entered already, but clearly haven't. I guess they don't want everyone to enter daily after all.

That happens a lot. I think some are timed, and if you try to enter again within a 24-hr period, even though it is the next day, it will say that. Maybe you can try again later in the evening. I know there was a Hallmark one that kept doing that to me.