On my Nexus 7 2013 Wi-Fi with Android 5.0.1 Lollipop I used the Slide setting for the lock screen. To experiment with a VPN, I switched to pattern lock.
After deleting the VPN entry I had created, I tried to switch back to Slide. However, the Slide and None options are grayed out and unusable under Settings -> Security -> Screen lock. Only the Pattern, PIN, and Password options are available.
How can I switch from Pattern to Slide?