Hi Santosh,
This sounds like an availability check is not being executed at all.
Check your settings in OPJK:
Plant <Insert your plant>
Order Type <Insert your plant>
Business funct. 1 (for creation)
Double click on the relevant entry and ensure that "No Check" is not selected.
If this does not help, then set a breakpoint at FM AVAILABILITY_CHECK_CONTROLLER and check if the breakpoint is hit when you execute CO01. If it is, then please post a screenshot of your CO09 here for the relevant material.