VPN service authentication problem in Android lollipop

I have developed a VPN client on Android using my own VPN service. It worked fine until Android v4.4.4. I am facing an issue in lollipop (5.0) when installing the VPN client after uninstalling and without restarting my phone.

The app does not ask for VPN authentication when trying to connect to the VPN server. But the same app works fine in kitkat. The VPN client asks for permission if we restart the phone after uninstalling the previous version or installing the current version. I have also tested this behavior in other vpn clients available on play store. The problem is also reproducible in other applications.

Does anyone know about this issue?