Hornafjarðarfljót bridge

Drove over the Hornafjarðarfljót bridge today, blue car rental website says to pay it in advance on the toll road website (spolur) which isn’t possible, and when I search my license plate on the same website, it says there’s no registered license plate matching. I read that it needs to be paid within 12 hours of driving over it and it’s been like 7 hours now and it’s not possible… any ideas what I might be doing wrong?