@DavidR
yes , it’s also good for me with my 2nd pc , same config , same avast , same firefox , and I really don’t know what happen on 1st
My login is good (id.avast), it’s after (my.avast)I can’t by-pass the loading

@Eddy
Right ,the problem is certainly on the side of firefox (conflict with my own system) , I asked for mozilla support , I’m waitng for now
On the other hand , trouble not so important , I only encounter this problem on my.avast , not on all my other https sites.
More , I can use firefox portable , chrome or even my 2nd pc to reach my account
But still a bit annoying when there is something I do not understand