Have you tried a different USB cord by chance ?
Also make sure the USB cable is laid down straight.
With no splits or cuts on it that will be one way for windows not detech it.
Provide me the model number for your seagate external drive.
If its not too much to ask, take a photo of the cable and the connector itself.
Once you do that we'll see about finding the right cord for the drive.
View this link so you can see what seagates recommends about your issue as well. Seagate Technology