Recently at Dublin when I tried to enter the security zone, for an Iberia Express flight, I couldn't get pass the scanner which was displaying a 'too early' message.

Although I'd checked in online and had a barcode on my phone, I wasn't able to get through about 3 and half hours before the flight. I did wonder if this was IB trying to limit the time in the lounge, or maybe it was just a general rule at DUB.