External drive not working on iMac, but works on Macbook Pro

I have read a few different threads relating to this question, with no real luck of a permanent solution.
I have an external drive that works perfectly on my Macbook Pro. My new iMac will not show the drive though (both with the current software).
The drive itself shows a power light and appears to be running/powered by the USB port.
I have tried several ports.
It does not show in Disk Utility.
The option in settings is set to show the drive in finder and on the desktop (I have checked this).
I have tried restarting the iMac.
I have also had this problem after the iMac has been turned off overnight, and turned on in the morning (and then plugging the drive in after powering on).
I resolved this issue once by turning off the iMac, removing the power cord for a few minutes, and powering it up again.
I don't think it should be something I have to do every time I would like to use the drive though - It would be very irritating if I had to do that every time.
Any advice or options here?
The iMac has only been used since Christmas day, 2014 - and has had this problem since that day (in which i solved it by the turn off/unplug thing).
Sorry, I am aware this question has been asked a lot. I haven't come across anything that is giving me a long-term solution to this problem.
Happy new year!

Some USB-powered drives are just crappy. They require too much current from the USB and cause the bus to fail or the bus can't provide enough power for it to fully spin up. You can often hear or feel them clicking periodically (like once a second) as they are trying to spin up.
If this is the case, a powered Hub, external power supply, or Y-cable will be necessary to consistently use the drive.

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