GigE Vision cameras can either be powered using an external power supply or by using Power over Ethernet (PoE). If PoE is supported by the camera. One of the more common reasons for a camera failing to be detected is that the PoE is not setup correctly. GigE cameras require a PoE injector, or GigE switch, that is compliant with the PoE 802.3af standard or adheres to the manufacturers specification. For example, here are the PoE specifications for two Basler GigE Cameras.
Note: Always check with the user's manual for your specific cameras regarding the power specifications.