this matter was reported by customer at first i thought that may cusotmer is exceeding its resource limitations. so i asked the customer to select less terminals in a conference with low resolution. but result was same.
then i thought may be the media boards are not online so i asked customer to make sure that their boards are online through display board command. but result was still the same.
then i asked customer to send me the license details. and when i check the license it was expired.