Contract at Object ID overview page vs fact sheet.

Hi

Object ID(Equipment) is entered in Object List of the Service Contracts line item. When I open this Object ID(Equipment) from Accounts&Products->Object,      it does not show Service Contract or relevant assignment block. but when I open the FacSheet for the same Object ID, Service Contract Assignment block is available with contract number.

What is the reason for service contract is not available at Object ID overview page level but available at fact sheet.

Thanks

Shaik