I must say - until today Seagate external HDD displayed in My computer immediately after connecting.
A little googling, I clicked on the My computer icon, then clicked on disk Management and my hard drive was discovered

But I did not understand why he does not appear in my computer?
If Yes, then I would be stuck G to a different USB connector and tried to change the letter. So, just to verify that the OS sees the disk as a whole.
If not, the USB connector damaged/clogged.
In addition it would be good to run chkdisk on this G from the second successful company. - Alfred48 commented on September 26th 19 at 07:27
Check Disk (.exe) is a program that checks files and the disk surface, and trying to repair the errors detected. Start Windows Explorer on the drive letter right mouse button, properties, tools, check disk - Alfred48 commented on September 26th 19 at 07:36