Hi @Minitintoy13,
Thank you for posting here in the community. I understand that you no longer have access to an old Google Account. But no need to worry, help is here.
To Set up Google devices such as cameras, speakers, displays, Wi-Fi routers, Chromecast products, and the Pixel Tablet's Charging Speaker Dock you will need to have or Create a Google Account.
While we don't support retrieving your Gmail/Google account or password, we can point you in the right direction. Our friends at Google Account Help Community are the perfect folks to help you with it.
Let me know if you need more assistance.
Regards,
Mario
