Possible cause and solution:
Make sure the activation path on Manage Activations > Find available activations lists the location from which the activation was originally borrowed.
Refresh the server. Click Advanced > Manage This Server > Refresh.
Determine if the clock on the computer providing the activation or the clock on the computer receiving the activation was changed since the activation was issued. If the time changed, set the time relative to the time the activation was borrowed. For example, if the activation was borrowed at noon and five hours have passed, set the client computer's clock to 5 PM and return the activation.
Click Manage Activations > Find available activations and make sure there is a borrowed activation. Sometimes activations are returned to the activation server, but still appear present on the computer that borrowed the activation.