Thunderbolt V3 (USB-C) to Dual DisplayPort Adapter - DP, 1.2 4K 60Hz

I can run my two external displays, each attached to its own Thunderbolt 3 port on my iMac. But... they will NOT connect through this device attached to a single of my two Thunderbolt drives. Same for another similar adapter I bought. The video signal is just not picked up by the adapter and fed to either of my two displays. Confusing to me - I can run two external drives each connected to their own single Thunderbolt port - but this adapter and another of its ilk will not pass the signal through to the displays when connected to a single Thunderbolt 3 port. I tried mightily, but just could not get this to work,UPDATEDidn't send it back. Mfr suggested using new cables. I didn't have any other DVI to display port cables, so tried my VGA to display port adapter. The adapter now works - two external displays up and running, in addition to the iMacs built-in screen.UPDATE 2.While I can run two external monitors from this device - it's ONLY in the VGA mode. Which is a bit "clunky" compared to DVI. Spent an hour with AppleCare last night. They couldn't figure out the refusal of the displays to pick up the video signal when attached to the monitors' DVI ports. They suggested I use "active" cables... so... I ordered some active Displayport to DVI cables. Should be here today. I'll let you know how that works.FINAL UPDATE:This works like a champ ..IF... you have the right cables. You DO need ACTIVE cables. The only ones I could find areCableCreation Active DisplayPort to DVI Cable, 6ft DP to DVI-I Cord, Eyefinity Support Multi-Screen:https://www.amazon.com/gp/product/B019Q7I2M0/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1So.. if you use an iMac and want to run two external displays from one of your two Thunderbolt 3 ports, this device works great, if you get the active cables

I expected it to be more of a hassle to set up. I just plugged it in and it worked. No drivers needed or anything.Great product.