Hello Pradeep

First of all, I really like the way you have described all the steps that you have followed and the issue you are facing; it really helps when providing assistance.

I have a Mac running OS X Yosemite 10.10.5 and VirtualBox 5.0.10. However,  I really do not think the versions matter here.

In addition to the instructions provided in the PVS Quick Start Guide, for Mac, you will need these settings:

Launch VirtualBox and remove the Pega Marketing/Decisioning virtual machine from the library. You can it again later (this is not absolutely necessary, but just a cleaner approach).

1. Go to VirtualBox -> Preferences (in the Mac top menu bar)
2. Go to Network tab.
3. Add a NAT Network under the NAT Networks tab (just click the + button on the right). It will be named NatNetwork by default.
4. Verify that there is a vboxnet0 network under the Host-only Networks tab. Edit and examine the settings. For your reference, my settings are as follows:
  Adapter Tab:
   IPv4 Address: Proprietary information hidden
   IPv4 Network Mask: Proprietary information hidden
   IPv6 Address: blank
   IPv6 Network Mask Length: 0

  DHCP Server
   Enable Server: Checked
   Server Address: Proprietary information hidden
   Server Mask: Proprietary information hidden
   Lower Address Bound: Proprietary information hidden00
   Upper Address Bound: Proprietary information hidden49

5. Save and exit from the preferences.
6. Now, add the virtual machine back.
7. Go to Settings > Network. If you have made any changes here, revert them to the way it was when you downloaded the VM. If you do not remember what changes you made, it’s best that you discard the VM, un-compress the VM afresh and add it to the library. Ideally, you will not need to make any changes to the network settings at the VM level.

Start the VM and let us know how it goes.

Good luck!

Regards
Guru