WSUS 3.0 Help needed

Guys, my WSUS server has been deployed and syncronizing with microsoft updates and with clients as well through GP but i have a problem it shows exclamation mark and cross on clients and also many corss and exclamation marks on many clients most of the updates are about 97 to 98% installed. I cant even find any log to understand the issue kindly someone help me with this what is this problem?