Spacewalk dosen’t install package unless “rhn_check” excuted on client

From Spacewalk server ( from UI), I could install packages on client only after executing "rhn_check" command on client; until then, it simply shows the action as pending.
Date and time are synchronized. Keys are working fine. I didn't schedule it to later time. I selected "Schedule action as soon as possible".

Of course we can write a script or something, but obviously something is wrong. I don't want to wait for 4hrs either.