Cannot ping interfaces after configuring uplinks as trunks.

I have a number of n2048p and am having the same issue so it's clearly something I'm doing/not doing.

I have 2 laptop's connected to a switch and running constant pings between them. I create the vlan, give the vlan int an IP address and add the switch ports to the access vlan. I can now also ping the vlan interface from both laptops. 

So far so good.

I now set the uplinks as trunk interfaces and everything stops working. The laptops can't ping each other or the vlan int.

Reset the uplinks back to access ports and it all works again.