I suspect the mount driver doesn't have the correct Windows COM port assignment, so there's no communication between computer and mount. The USB-COM adapter cable can be plugged into any USB socket on the laptop, A virtual COM port is created by Windows and is assigned a specific COM port number. The mount driver needs to know which in order to talk to communicate. So, you must enter the appropriate COM number into the mount driver interface. The COM number for the USB socket in use can be found by opening Windows Device Manager.
So, open Windows Device Manager, where yo'll see a list of all the devices used by the computer. Look down the list for >Ports (COM & LPT). Click on the > to expand it and you'll see a sub-list of virtual serial ports, each with a description and COM number. Find the one related to your USB adapter cable and note the assigned number
(i.e. COM1, COM2, COM3, etc). Close Device Manager and start PHD2. Open the Connect Equipment interface and you'll see your mount driver name in the Mount selector. To the right of this, click the its 'tools' button, which opens the driver interface. Somewhere on the driver interface will be a field to set the COM port number. Enter or set it to the one you just noted down. Close the tools interface and press the Connect All button. Test the communication between PHD2 and mount using something like the Tools/Manual Guide option. The mount should move accordingly.
Note that the COM number will change if you plug the mount cable into a different USB socket. So if you tend to swap things around you must ensure the driver knows where to look.
Hope this helps,