I am afraid that the provided information is not enough to find teh problem and I will need to examine a reproduction setup. The only thing I can assuem that might be happening is that some sizes are not correctly configured and the content is actually rendered but with little size and thus - not visible.
This being said, I would like to kindly ask you to prepare a sample, fully runnable, stripped down reproduction demo, open a new support ticket and send it to me along with detailed explanations and reproduction instructions and I will do my best to help.
On a side note, forums are considered public resources and we do not guarantee and on time response here and if you want to ensure that you will get a fatsre response you should open supprt tickets.
the Telerik team