1 TB Passport Not Recognised any more on iMac

My 1 TB passport is not recognised on my iMac anymore, but is recognised on my Powerbook Pro.

I initially formatted the drive in FAT32 so that it would be recognised by PC and MAC and have used it for years on MACs and PCs with no problems

All other PCs and computers still recognise the drive, except for the iMac. The iMac OS has recently been updated to Yosemite but so has the Macbook pro, which can still access the drive.

Any ideas please?


It is possible the computer is not providing enough power to spin up the drive. Make sure you are using the provided USB cable. 

Hi Hamlet

The disk is powering up Ok - the light remains on constantly. 

I am using the recommended cable. The drive works fine on all other computers.

I have spoken with Apple and they have walked me through vaious resets, but the problem remains on this iMac.

I have tried the same USB socket on the iMac with another drive and that works fine.