1) Does it matter what USB connections you use?
2) I have a Seagate 4TB USB drive and it would NOT turn off initially, but then I found software from the Seagate sight that I ran which updated the firmware inside the unit. After that it would go into STANDBY MODE.
Check and see if there is a piece of software that allows you to modify this.
3) *I thought drives entered STANDBY based on the POWER SETTINGS you assigned. I set mine to 20 minutes, so if any HDD isn't used for 20 minutes it goes into standby.
So go into your POWER SETTINGS and see what it's set to.