Just tried it on my win10 Home 64bit, firefox and avast free again with no problem.
I do notice that it has a Cookie policy initially at the top of the screen, which I closed. I manage cookies with CookieMonster add-on and firefox settings to block 3rd party cookies.
With CookieMonster I allow session cookies only for the site and when firefox closes, my firefox removes these cookies when it closes. I don’t know if anyone with a more strict policy on cookies, not allowing them at all would result the sites not being displayed. That just sounds too severe action by a website though.