I am having the same problem. I am running lollipop (cyanogen) on my HTC 1 m7. After I installed the ROM, there was no play store, so I downloaded the apk. The icon shows up, but when I click on it, a white pane pops up for a second like it's going to open, but it doesn't. I'm back on my apps screen and there's no error message or anything. I can browse and do everything else; just no play store. When I try downloading from the online play store, it says apps will be installed to my device soon. But it lies. Any suggestions?