had the same problems yesterday and some today. Looks like yesterday I got credit fo about 1 of every 2 or 3 codes I entered (ended up with 21 credits, of the 25 needed for the contest and I ran radio for almost 9+ hours),

Today I have 9 credits after about 3.5 hours.

I keep deleting cookies, restarting it and also hitting the submit button instead of enter to see if that helps