My book 3tb

Hi i have a my book 3th for pc that i use on a mac.I bought a 25ft usb extention for it but it will only stay conecte for a few minuets and then it disconectes all by its self and it comes up on my mac disk up conected improperly and then my drives light shuts off but my drive is still running and when i hold the power buttonon the drive it wont turn off i have to unplug the power supply and plug it ack in.If you know what the problem is PLEASE help me

One problem is WD does not recommend using a USB cable longer than the one supplied.


Okay thank you