Setting up wired Airport Express for airplay only (I know, I know)

I do have an AirPort Express here to test and can help with the setup of your AirPort Express.

Although it might seem unintuitive, the correct initial setup of your AirPort Express will be to "Create a new network". This is the only option that you have that accommodates an Ethernet connection from your main router to the AirPort Express.

Bridge Mode is automatically configured when you go through the setup. If you don't want to use the Wi-Fi network that the Express is creating, you will have the option later to turn off the Wi-Fi network, so the Express will operate only as a wired Ethernet network device.

Yes, all this seems confusing. But, things will work......assuming the AirPort Express is functioning correctly.....if you want to proceed.

In the meantime, you might want to continue working with Tesserax though to see things through.

Ok, thanks for clarifying that for me.

To start, I suggest that you perform a "factory default" reset on the AX. Once completed, go ahead and connect it by Ethernet to your TPLink.

Ref:  How to reset your AirPort base station - Apple Support

In this default configuration, the AirPort Utility should now "find" the AX and you can set it up either via its "automatic" or "manual" setup steps. I typically use the second method so that I can "fine-tune" the settings. In this case you want to reconfigure it as a bridge.

The Express has been very reliable over the years, but it's always possible that a power surge or static electricity has damaged the port. But, if that were the case, Ethernet would not work at all. It would not work some of the time and then work at other times.

The Express that you have was introduced in March 2008 and discontinued in June 2011, so the product is at least 12 years old and as much as 15 depending on when it was placed into service. I suppose that it is possible that an internal component is acting up, but troubleshooting something like that is extremely difficult because you literally have to saw open the AirPort Express case along the seams to open up the product.

I don't have a Mac running Monterey here, but I did check the old Express that I have with a Mac running Ventura and had no problems setting up the Express to create a new wireless network.

If the Ethernet cable works OK with your Mac, then you have to assume that the cable is good.

Start over and perform a Factory Default Reset on the Express

Connect an Ethernet cable from a LAN <--> Ethernet port on your main router to the Ethernet port on the Express

Click on the Wi-Fi icon at the top of the Mac's screen and look for a listing of New AirPort Base Station

Just below that listing, click on AirPort Express

That will start up the AirPort Utility setup "wizard" automatically. The utility will take a few seconds to analyze the network and then display a screen that looks like the example below.

Network Name......Type in a name for the Wi-Fi network

Base Station Name.....Type in a device name for the Express

Password....Type in a password

Verify......Type in the same password again to confirm

Click Next

If the Express is working correctly, the Express will display a green light in about a minute and the setup is complete. Later, you can turn off the WiFi on the Express by using AirPort Utility. Post back if you are not sure how to do this.

No, bridge mode is correct for this configuration. Otherwise, you would have two separate subnets ... not something you would want for using AirPlay ... as AirPlay is not easily routable.

After the reset, and with the AX still connected by Ethernet, it is discoverable by the AirPort Utility ... correct? Have you tried bypassing the "automatic" setup, and try manually configuring it for bridge mode?

No need to be sorry, I'm glad to help where I can.

Let's try doing this the "manual" way. Will you be using a Mac, PC, or iPhone for the AirPort Utility? You mentioned that you have an M1 MacBook Pro, so I'm going to assume you will want to use that.

As such, here would be the steps to try:

1. Run the AirPort Utility, and then, select your AX.
2. Select Edit.
3. On the Network tab, change the Router Mode to: Off (Bridge Mode)
4. Select Update, and allow the AX to restart.

Sorry, I don't have an AX handy, but this screen shot is from the AirPort Utility with my Time Capsule. Regardless, the menu options should be similar.

Power off the main router

Power off the AirPort Express

Restart your Mac

Power up the main router and let it run a minute

Power up the AirPort Express

The "update" is more than 4 years old at this point. It won't hurt to try to update the Express, but I don't think it will help either. If you continue to have problems with the Express, all that I can suggest is try another AirPort Express. You can find them on eBay. Try for an A1392 model of the Express, which was discontinued a little over 5 years ago. It will run much cooler than the A1284 version.

Just to understand. Is your goal to connect this AirPort Express base station to your existing network by Ethernet or by wireless? I'm asking because your post's title mentions "wired," but you are stating that you have "assigned the 2.4khz network for the AX." I assume by the latter you meant 2.4 GHz ... correct?

If you give the Express the same Wi-Fi network name and password as your "main" network, you can "expand" the coverage area of your main Wi-Fi network......if you need to do that.

Or, just set up a "temporary" Wi-Fi network and password if you feel that you will want to manually turn off the Wi-Fi capability of the Express once it has been set up initially.

Thanks to Bob, you got a real AirPort expert on-line with you now.

One small add to Bob's comments is that even if you disable the AX's wireless radios, AirPlay will still work. That is because AirPlay will work over either Wi-Fi or Ethernet. In this case, when you use AirPlay to stream, that stream will first go to your TPLink's wireless network, and from there to the AX over Ethernet ... so having the AX's wireless radios operating will not add anything to the equation.

... and I believe, AirPlay was your main goal with this AX.