There are different limits in the game that you might have reached.
The amount of Resources you can get from each Castle is limited - 50 000 Resources a week. You can raid the same Castle only once within 7 days.
You can also gain up to 500 000 Resources from different Castles a day. It includes Resources gained from Raids and as Gifts via the Caravans.
Another important thing to remember is that the basic number of Raid attempts is limited as well - a maximum of 10 attempts. You get new Raid attempts every 2.5 hours.