An addendum to a previous post that gives additional details if you're still having trouble deploying your Unity games to an Android device.
About a year ago, I made a post which walks you through the steps to start testing your games on Android: Deploying Unity Games to Android. Everything has been working just fine up until recently. I wasn't sure if it was my recent update to Windows 10 or perhaps some update I'd taken on my Nexus 5. After some head scratching, I managed to figure out you need to check one more setting I neglected to mention in my last article.
This is probably specific to those connecting their phone to a Windows computer. You need to be sure your phone is connecting using PTP, which stands for "Picture Transfer Protocol". For some reason mine had switched to MTP or "Media Transfer Protocol". It's easy enough to double check if you're having trouble deploying Unity games to your device.
From the main menu on your device, open the Settings menu.
Find the Storage settings menu and open it. Tap the upper right button to open the context menu. Within that menu, select "USB computer connection".
Once you're in the "USB computer connection" menu, tap the option for "Camera (PTP)".
This got me back up and running. It's definitely worth checking if you start having trouble deploying games to your phone.