Symantec Endpoint Protection Manager (SEPM) takes 3 to 5 minutes to login. Moving around tabs in SEPM admin experiences delay of up to 10 seconds to completely switch and load new tab. Failed client registration attempts can be seen in ersecreg.log.

Failed client registration attempts can be found here: C:\Program Files (x86)\Symantec\Symantec Endpoint Protection Manager\data\inbox\log\ersecreg.log

5 Server returned: 469

5 No data from server.

SEPM is running on Virtual Machine (VMware)

SEPM Web Console

The guest operating system is Windows Server 2012, or later

The virtual machine is on hardware version 11/ESXI 6.0 compatibility

The virtual NIC is vmxnet3 and the driver version is 1.6.6.0 and newer

The Receive Side Coalescing (RSC) feature is enabled globally and on the vmxnet3 adapter.

A VMware defect causes performance degradation for some client/servers workloads.

The issue can be resolved by upgrading to VMware ESXi 6.0 Update 2.  For workaround please see After upgrading a virtual machine to hardware version 11, network dependent workloads experience performance degradation (2129176)