cannot enter vsphere license

Hello,

We are upgrading vsphere 4.1 to vcloud suite 5 standard .  After upgrading vCenter to vcenter 5.0  we started upgrading ESXi to 5.0 , but we are unable to add the new vsphere key  .we got the folloging message

"license error: 5 Diagnostic message:license file not found"

Any idea please

Thanks