Airport blinking light - tried EVERYTHING...HELP!

What is the exact model number of your Arris modem?

When you get the flashing amber status LED, what are the exact errors that the AirPort Utility has identified?

When you "power cycled" do you do something like the following AirPort User tip? Did you experience any type of power outage or brownout?

Modem Model

Arris TM902A

Thanks. I just wanted to be sure you had a simple modem and not a combination modem/router or gateway device.

Errors

The Airport Utility shows the Extreme blinking yellow. It has a red circle with a 1 in it. The error is "Internet Connection". Clicking on that reveals a popup that says the Extreme hasn't been assigned an IP address and won't be able to connect

This typically indicates that your modem & the Extreme are not "communicating" with each other. There could be a number of reasons for this. Since this was working before, we know that it should not be a compatibility issue between the two devices. Instead there is either a configuration issue with the Extreme or a failure of either, the Ethernet cable being used between them, or the Ethernet port on the Extreme. Trying another known good cable would be a good measure, even if you used the existing cable (between the Arris & the Extreme) with your Mac Pro.

Power Cycling

I didn't follow your guide, I just found that this morning. That's on my list of things to do when I get home.

Please perform this in its entirety and post back your results.

Power Issues

We had a few scattered thunderstorms the night before this fiasco. I recall one distinct clap of thunder that was very loud. However the modem and Airport Extreme are plugged into the same surge protector so I assume both would be fried if lightning was a factor. Also no other electronics are acting weird and we never lost power. At least not enough to cause any blinking clocks.

Although a reasonable deduction, this may not be the actual case here. First, a surge protector will NOT always protect your sensitive networking hardware. It would depend on the amount of electrical surge caused by a lightning strike. Second, these can happen so quickly that the "fuse" in the surge protector may not "blow" in time. In this case, it may be possible that the Arris was more tolerant to the surge than the Extreme was.

ses_mac wrote:

However the modem and Airport Extreme are plugged into the same surge protector so I assume both would be fried if lightning was a factor. Also no other electronics are acting weird and we never lost power.

A surge can be incoming to every appliance on AC wires. A surge hunts for earth ground. It is electricity. If no outgoing path exists, then no damage. You surge was incoming on one wire. Apparently it found the best path to earth destructively via the modem. That is typical especially when the ISP's wire would already have best protection.

A surge found a best path to earth destructively via a modem. That was the best path meaning all other appliances were protected by that modem.

Protection is always about how an electric current connects to earth. An adjacent protector cannot and does not claim to protect from that type of surge. It has no low impedance connection to earth. It can even make damage to adjacent appliances easier. Protection is always about how that current connects to earth.

Your ISP cable would already connect to earth where it enters the building. Damage happens when both an incoming and outgoing path exist. Incoming to everything on AC mains. Outgoing to earth on a best path - destructively via the modem. Damage because you did not earth that incoming surge at the service entrance. Your example is why informed homeowners earth a 'whole house' protector.

No protector works by blowing a 'fuse'. Surges are done in microseconds. Fuses blow in tens of milliseconds or longer. How does a miilimeters gap in a fuse block what three kilometers of sky could not? Myths exist when one knows by ignoring numbers. Destructive surges are hundreds of thousands of joules. How do near zero joules in a plug-in protector absorb surges that are hundreds of thousands of joules? It doesn't. It does not claim protection that is only assumed using subjective (ie junk science) reasoning.

Lightning can be 20,000 amps. So a minimal 'whole house' protector is 50,000 amps. Because protection from direct lightning strikes is routine - when properly earthed by a low impedance (ie less than 10 feet) connection to single point earth ground.

This will not solve what may have been a modem acting as a surge protector for everything else. But this is required to avert future damage. And to protect those near zero, adjacent protectors.