similar problem for me too
I have enabled ALL cookies, but not know about the private browsing, unless it is to do with VPN, then I do..But currently not using a VPN.
For example: Top right of screen LOG IN: enter valid data, response is THANK YOU: but the valid log in not reflected in the Welcome block.
Also If I do manage to get in, and try to post, when I have ended my missive, I am told I am not logged in.....
Help please....ssa