In some cases, a device will not communicate with the Notification Server. It will not send basic inventory or refresh policies/update configuration. This occurs when using a USB connection to a host computer that can resolve to the Notification Server.
It may also be noted that it is not possible to browse to the Notification Server.
It appears that this is due to a proxy setting on the device itself.
There are two steps to ensure that the device can browse and access the NS. This does not seem to be universal nor permanent.
In ActiveSync on the host computer, drill down to Tools > Options > Advanced in Active Sync and select The Internet from the drop-down menu.
Disable the proxy on the device. Some devices, the ATT 8525 for example, have programs to enable and disable the proxy. There is also a registry setting in WM5 that can be modified, as described, below.
The default setting (that uses the proxy) is: "EnableAutoDetect"=dword:00000000
Change it to: "EnableAutoDetect"=dword:00000001
Or simply delete it. It's more of the fact that if it's there and =0 it's used. If it is missing, it is not used. But changing it to =1 will also make it disable. This way you can simply change the value back without re-adding the seting back in.
For some reason, the registry entry above will occasionally revert from =1 to =0, causing Internet Explorer's proxy to be active again. Deleting the registry entry prevents this from happening. Certain programs may recreate this entry.
Notes: When using the USB passthrough, the computer's network connection is being used, which does not have access to the wireless Proxy. If the proxy is enabled, all requests in PIE will try to go through the proxy and will time out as there is no access to it. If the proxy is disabled, the device will access the internet directly using your computer's connection. The proxy re-enables itself when the USB connection to the computer is disconnected.