Change Tier causes network problems

Hi I changed one on my VMs from A2 standard to A3 standard. Upon reboot the machine has network problems as follows:

Local subnet and others VMS on same subnet - communication is fine

Internet Access - fine

However, the machine is no longer accessible (on any port) from my on premise network across the site to site vpn (using juniper SRX).  Other VMs in azure are just fine and the VPN for them is all ok.

Anyone have any ideas? 

(I have checked firewall, rebooted a few times, tried changing tier back and forth to no avail).

thanks in advance for any ideas