I logger-in, to stackexchange, on a different computer. I am in https://area51.stackexchange.com/users/115681/ctrl-alt-delor it is showing me logged-in. I then go to the stackexchange menu, it shows me My Sites. I then select a link to another site, it takes me there but I am no-longer logged-in. When I return I am still logged-in.
It appears that I am not logged-in on all of your sites.