Unable to add Logitech doorbell to Home. Home says accessory already added.

Hello massimo280,

Thank you for reaching out to Apple Support Communities, and we'll be happy to help in any way we can. We understand you're having issues with adding an accessory to HomeKit. Try the steps listed here to see if they resolve the issue: Add an accessory to the Home app - Apple Support

"Before you add an accessory

• Update your iPhone or iPad to the latest version of iOS or iPadOS.
• Make sure that your accessory is powered on and nearby.
• Check the accessory's manual to see if it needs additional hardware to work with HomeKit or Matter.

Add accessories with your iPhone or iPad

To add an accessory to the Home app, use your iPhone or iPad. You can't add accessories to the Home app on Mac.

1. Open the Home app and tap Add  .
2. Tap Add Accessory .
3. Use the camera on your iPhone or iPad to scan the eight-digit HomeKit code, or QR code on the accessory or accessory documentation. If you have an iPhone 7 or later and see  on your accessory, hold your iPhone near the accessory to add it.
4. When your accessory appears, tap it. If asked to Add Accessory to Network, tap Allow.
5. Assign your accessory to a room and name it to help you identify it in the Home app and control it with Siri.
6. Tap Continue, then tap Done.

You must set up a home hub to add Matter accessories to the Home app.

Some accessories, speakers, and smart TVs might require software updates or additional setup with the manufacturer’s app.

Samsung AirPlay 2-compatible smart TVs don't support HomeKit and can't be added to the Home app."

We hope this helps.

Cheers!