Smart Accessories No Longer Connecting to Home App

Has anyone else experienced a sudden, persistent "No Response" or connection failure with HomeKit enabled accessories that previously worked perfectly?

I am currently stuck and looking for any insights the community might have. A few weeks ago, several of my devices (specifically GE Cync lights and a Tapo smart plug) dropped off my Home app. Both had been working seamlessly with my HomePods and Siri commands for quite some time.

The Situation So Far:

• Manufacturer Support: I have been in contact with both GE and Tapo. Both companies are stumped because the devices appear functional but simply will not handshake with the Home app.

• ISP Advice: My internet provider suggested a new router, but I am hesitant to go that route without confirming a hardware failure since other devices are fine.

Troubleshooting Already Completed:

• Reset all affected accessories to factory settings.

• Deleted and recreated my Home scenes.

• Set up a temporary, dedicated 2.4GHz network to rule out band steering issues.

• Disabled iCloud Private Relay and Limit IP Address Tracking in Wi-Fi settings to ensure local discovery is not being blocked.

• Restarted all Home Hubs (HomePods).

Despite these steps, I cannot get them to reconnect. It feels like a software handshake issue within the HomeKit ecosystem rather than a hardware fault.

Has anyone encountered this specific wall where standard troubleshooting fails? If you found a fix (whether it was a specific iOS setting or a router configuration) I would love to hear about it.