Precision T3620 Intel AMB MEBX does not appear in BIOS

I have a Precision T3620 with a Xeon E3-1270 CPU (which, per Intel, support AMT). 

MeshCmd.EXE AMTINFO reports:

Intel ME v11.8.97, pre-provisioning state.
Wired Enabled, DHCP, 00:00:00:00:00:00
Connection Status: Unknown, CIRA: Disconnected.

MeshCmd.EXE AMTVERSIONS reports:

BIOS Version = 2.3.5
Flash = 11.8.97
Netstack = 11.8.97
AMTApps = 11.8.97
AMT = 11.8.97
Sku = 0
VendorID = 8086
Build Number = 4739
Recovery Version = 11.8.97
Recovery Build Num = 4739
Legacy Mode = False

So, the system does appear to have AMT.

In the BIOS setup, there is an option (which is checked) to cause the MEBX hotkey to be enabled.

But Ctrl+P (and Ctrl+M, Ctrl+I) do nothing, and the F12 boot selection menu does NOT list MEBX.

(There IS a BIOS Admin password set, and I also tried UN-setting the BIOS Admin password and then setting it again. It made no difference).

How do I get to the BIOS MEBX page so that I can set up and enable Intel AMT on this Precision T3620?

thank you,

Jay