If your network Pool is VCDNI based, you need to ensure a few things:
1. that the vLAN 220 actually exists in the network fabric
2. vLAN 220 is trunked to all NIC Ports associated to the Distributed switch that backs the Network Pool
3. Ensure that your network supports an MTU of 1524 ... if it doesn't set the MTU of the network pool to 1476, and recreate anything that used that network pool thus far (to get the new MTU size).