@Asyn : no , issue resolved yesterday , DST Is not involved
however it seems to be a clock (bug?) issue in latest ff versions.No more trouble with FF<50

@DavidR : sorry if I misunderstood , but there are nothing against avast , no more against kind of avast version , no more about kind of OS we can use
Right , I’m using 17.2.2288 on same windows xp than I posted first , with latest firefox version 52.0.1 ESR (same with v52.0.1 without ESR)
Issue comes from a change of mozilla since their version 50
I just want people using my.avast account with FF52 regardless of their OS to try to manualy advance their windows clock (10 minutes or 1 hour)
As far as I try to loggin my.avast with win xp , win7 or w8 (do not have w10) , everytime The account link remains blocked
Back to real time , and all is right.
I just wanted you to experience, no more and no less :wink: