When I start a Genymotion emulator (Android studio emulators crash android studio and dont start), I have to run adb connect 192.168.56.101:5555 in order to connect adb to the emulator. Otherwise it doesn't show up when I use adb devices. I never had to do this before and I cannot figure out why.
Looks like it has something to do with recent update in android sdk platform tools. Downgraded mine from 28.0.2 to 28.0.1 and successfully got my genymotion emulator in adb devices back.