Tried to download, cannot find it, will not run

I have one week old iMac (November 2016). OS Sierra 10.12.1 — a 4GHz Intel Core i7 processor, 27-inch 5K retina display, 16GB DDR3 with a 1tb OEM SSD. Wanted to test my WD My Book Pro 16Tb over Thunderbolt 2. Clicked download for the Blackmagic Disk Speed Test software on the App Store. It seemed to download. Clicked Open on the app button. Nothing happens. Cannot find the software in the download folder, app folder or the utility folder. Something is shady when as many reviews rate it as 1-star as rate it with 5-stars.

IcePickPlaya about Blackmagic Disk Speed Test, v3.0