Apple Watch - Setup Accessories Using The Home App On Your iPhone

After moving to my new Apple Watch, I tried to use Siri to turn off a light, but the watch said I had no HomeKit devices set up, even though I knew I did. When I checked the Home app on the watch, it prompted me to set up devices using my iPhone. I had previously migrated to new watches without this problem and hoped it would resolve itself, but it didn't. I found limited information on this issue, with most articles discussing the device not responding to a Siri command. While figuring out my next steps, I did an Apple Fitness+ workout, but the AppleTV couldn't find my watch. I started to think they might be linked.

Eventually, I discovered my watch wasn't signed into my Apple ID, which I realised was step 5 in the setup. I’m not sure why the restore didn’t sign me in or remind me later, but signing in fixed the Home app and Apple Fitness+. While checking for other issues, I noticed my Apple Pay wasn’t working. When I double-pressed the side button, I only saw store cards and no payment cards. Even though the cards were saved and I had entered the CVV numbers during restore, the issue was that the address and email weren't selected. After selecting them, both my credit and debit cards worked on the watch.