Old Time Capsule. New Network

Sorry, I am confused.

If you reset the Time Capsule back to default settings, that would have erased the previous Wi-Fi network signal that the Time Capsule was storing and creating, so of course you would not be able to find the Wi-Fi network.....because it is no longer there.

The Time Capsule needs to be reset again using a Hard Reset or Factory Default Reset and then set up again if you want the Time Capsule to create a Wi-Fi network signal.

Post back if you need step by step for this.

Glad it seems to be working. As Bob Timmons suggests, let's be sure that you can in fact connect to the Internet...if that's all working properly, then the blinking amber light is probably the visual signal of the Double NAT warning you mentioned in Airport Utility.

Double NAT is an easy fix - you will just need to decide what device is going to be your router and issue IP addresses to your devices. Since your setup (if I recall correctly) is that this Time Capsule is in a remote studio/shed to extend your network, you probably will want to put the Time Capsule in the mode where it is only an access point and not providing IP addresses.

To do that, in your Time Capsule's configuration settings (accessed through the Airport Utility), you will want to keep the Wireless tab settings as they are (with your same current network name, etc - I mean, you could change those if you wanted to, but why?). You will want to go to the Network tab and set it to "Off (Bridge Mode)" to turn off the DHCP server that assigns IP addresses to devices.

Then your TC will just be an access point that extends your existing home network with WiFi to your shed.

I think I'm confused too...

If I read your description correctly, you have Internet from your UK service provider and the network in your house is extended to the studio by Ethernet. You had your Time Capsule WAN port plugged into the Ethernet, and also had working Wifi which showed up in Airport Utility and was the same network name it always was - but then you reset the Time Capsule?

I don't understand why you did that. Did the network not show up in System Preferences or did your computers not connect to it? But as Bob Timmons says, you have now deleted the working Wifi network and need to set up the Time Capsule as a Wifi access point again...

AirPort Utility User Guide for Mac - Apple Support (CA)

This is really confusing.

The network that shows up is my old one from the USA but it isn't working.

Oops I just tried it and it works!

Let's first have you clarify that things are working, and then we will tackle the slow blinking amber light.