You can try contacting Google Nest Support starting with this link: https://support.google.com/googlenest/gethelp
Or you can see if Google Nest's install video helps, starting at 1:00 in the video: https://support.google.com/googlenest/answer/11003780?hl=en
Or you can share what exactly is happening when you try to add your floodlight camera in the Google Home app, so customers reading your post can try to assist you. For example, Are you prompted for your QR code? Or are you selecting the "Continue without scanning" option? What happens then?
Just checking in to make sure that you've seen our responses. Please let me know if you have other questions or concerns as I will be locking this in 24 hours if I won't hear back from you again. Feel free to start a new thread and we'll be happy to help.