No Inspection plan could be found

Hi Guru's ,

We have inspection lot created on 12.01.2014. Lot is in status CRTD CHCR SPRQ. For material we have two inspection plans. For one inspection plan Valid from date is 08.05.2014 & for another inspection plan valid from date is 04.05.2014. Material assignment is done for both the plans. Check boxes post to insp. stock., Insp. with task list, Automatic assignment & check chars are selected for insp. type in material master. In material assignment for inspection plan key date is shown as 09.05.2014.

When the user tries to assign the inspection plan by entering the key date 08.05.2014 system gives error No inspection plan could be found. Inspection plan usage is 5 & both the plans are released. lot size for both the plans is correctly maintained.

What could be the reason for error?

Regards

Amit