Some VM don't recognize virtual network cards

Hi all,

I have an hyper-v install with a dell T320 server with two ethernet cards from Broadcom and Windows Server 2012 R2 as hyper-v server.

I have one VM with 2012 R2 and one another host with 2012 Std. All the systems are working fine since we make the install.

Since this morning I see that the 2012 Std server is not able to connect to the network.

I shutdown all VMs, delete the Vswitch, delete the physical network card, restart the host, recreate a new vswitch and reconnect the VMs to it. I access the network on 2012 R2 but in 2012 Std the OS see no network card.

What can I do.