2 hard drives WD 4TB MyBook on one computer

Hi, I have 2 hard drives WD 4TB MyBook.
I can not connect the two hard drives at the same time on a computer. Only recognize one.
If I connect both separately, the system recognizes. But together, I can only access one.
Windows tells me that another device is connected, but does not appear in the browser.
My operating system is Windows 8.1. I tried several (modern, i7, 8GB of Ram …) machines.
How I can have the two hard drives running on one computer? With hard drives of other brands this is perfectly normal.
Thank you very much!

It’s a Windows issue this explains the fix  https://wdc.custhelp.com/app/answers/detail/a_id/6571


The link to the solution seems to go to a blank page. I have had this problem for the longest and am not determined to fix it. And it isn’t only the recognition – when I got it to recognize, the automatic back up failed.

You have to scroll down about halfway.