This is a known issue affecting vCenter Server 5.5 and 6.0.
Currently, there is no resolution.
To work around this issue, apply one of these options:
- Use the vSphere Client to access the virtual machine console.
- Assign Read Only permissions for the user(s) who need to access the virtual machine console on the ESXi host.
Note: If the ESXi host is part of a cluster, you must assign permission to each host of the cluster.