ID:176676 Either the positive pin "<name>" or its complement pin "<name>", or both, might have constraints and therefore fails to fit in the device "<name>"

CAUSE: The Fitter found the location for the positive pin. However, the location for negative pin cannot be found. Either the specified positive pin or its specified complement pin, or both, might have constraints and therefore fails to fit in the specified device.

ACTION: Check and if necessary, remove some constraints on either the positive or the negative pin, or both of the differential pair.