If you have connection timeout issue of Yeelight Lightstrip, and the strip has shown in your router’s DHCP list, please have a check if your xiaomi account is bigger than 4294967295 (32bit). If so, you can have a try with the following:
1、Logout your account and login with account: firstname.lastname@example.org, Password: yeelink1234 from Yeelight application.
2、Try to connect device with the account. Update firmware once connected, then reset your device and try again with your account.
It would be great if you delete the device from Yeelight after firmware updated.
You can find xiaomi account and firmware update item from the pic.