i cant create the Knights' hall

[joylogan]

Please help me i can not create the Knights' hall, i have completed the Trials & Tribute Goal, but not cant build the knights hall. that sends me a message "you're at your limit!, level up to build more structures of thi type"

[fwlbdrafter]

You have to sell a royal building. I had the same problem and had some towers in storage, I placed them out and sold them and was able to place my knights hall then.