I recently acquired two Lenovo M58p desktops and set up vPro in Small Business mode. It worked fine when the computers were on, but once turned off, I could no longer access vPro by browsing to http://<ip_address>:16992. What gives? The main thing I need vPro for is accessing machines that are powered off!
Turns out by default, this vPro (5.1.0.0020) only allows accessing machines that are ON (power state S0) or in sleep mode (power state S3). To allow access in hibernated (S4) or powered off (S5) states, you have to change this setting:
Intel(R) ME Configuration
> Intel(R) ME Power Control
>> Intel(R) ME ON in Host Sleep States
Set that to Desktop: ON inS0, ME Wake in S3, S4-5:
Once I made that change, I was able to browse to http://<ip_address>:16992 even when the computer is powered down.
Background info on vPro and power states: AMT Power Policies.