iPhone 3g doesn't show up in find my iPhone
I currently have 3 devices set up on mobile me account (iPhone 4 and two ipads). I just re-activated my old iPhone 3g. I restored the phone to factory settings and installed the latest OS (that's available for that phone). The phone is fully functional (ie, make/receive calls, use 3g internet,etc).
Under the mail, contacts, I added my MobileMe account and enabled Find My iPhone. However, when I login to find my iPhone, it only finds my original 3 devices. I've tried disabling, then re-enabling it. I've tried deleting the account, then adding it back. All to no avail.
Any ideas what the problem is, or what else I can do to try to fix it?
iPhone 3G, iOS 4.2