I have changed the password on my wi-fi and now my Airport base station doesn't not appear in the AirPort Utility. How do I solve this?

I'll give that a try.

Tesserax has great advice. I really meant to say that if you cannot "temporarily" connect the Express to your Mac using a wired Ethernet cable connection, then you should start over again. You could use any spare Ethernet cable.....any length will do.....to temporarily connect the Express. Once you have changed the password, you can move the Express back to its normal location.

If the Ethernet connection still won't allow the Express to appear in AirPort Utility, then your only option at that point would be to start over and reset the Express and then set it up again using a wireless connection.

On what device did you change the wifi password?

Are you now connected to the wifi via the airport on whatever device you are running?

It will depend on if you are doing this on a Mac or iOS device.. so fill in those details and it should be fairly simple.

A real Mac.. ie one with ethernet port.. please plug it into the airport so you can bypass wireless .. you just cut off the branch you were sitting on.. if you change wifi password via wifi your airport utility has lost the ability to connect.

What is the make & model of your router? If it is another AirPort base station, for future reference, you should change the password on the extending/joining base station first, prior to changing it on the "main" one to avoid this.

In this case, you can simply reset your Express, and then, set it back up again. Have you tried that yet?

I have changed the password on my wi-fi and now my Airport base station doesn't not appear in the AirPort Utility. How do I solve this?

If you are saying that the AirPort Express connects to your main router using a wireless connection, and you changed the password on your router.........then the AirPort Express is still programmed to connect to your wireless network using the "old" password. So, the Express is lost and does not know what to do. AirPort Utility will never find the Express unless you connect your iMac to the Express using a wired Ethernet cable connection to change the "old" password to the "new" password.

As Tesserax mentions......and it is water under the bridge at this point......you should have changed the password on the Express first, then changed the password on your router.

If you cannot connect the iMac to the Express using a wired connection, then the simplest solution would be to reset the AirPort Express back to its original default settings using a Hard Reset and then set up the Express again to connect to your network.......just like you did the first time that you originally set up the AirPort Express.

That way, the Express will pick up the correct settings that it needs to connect to your wireless network using the new wireless network password.

Ok, in this case the Express can only join the wireless network provided by the Netgear, not extend it.

I suggest that you temporarily bring the Express over to where the Netgear is and connect it by Ethernet. You should then be able to "find" it with the AirPort Utility to make the changes.