I have problems with loging on my avast accaunt. When I trying to sign i recive this message “The username or password you have entered is incorrect.”
I use option Reset Password and change pass but that not help me.
https://s21.postimg.org/g761uz86v/avast_00.png
Where are you doing the sign-in ??? my.avast.com or the Avast User Interface ???
You should use the my.avast.com link. 
I tray to log on my Avast User Interface but dont allow me. Then i tray on https://my.avast.com and i have some problem there. When i use option Reset Password system automatically log me on myavast, but when i make log of i canot log on i constantly receives a message that username or password is incorrect
Once you’ve logged in with the temp. password, you need to change your password:
http://screencast-o-matic.com/screenshots/u/Lh/1473000347545-74523.png
http://screencast-o-matic.com/screenshots/u/Lh/1473000375567-99133.png
Once this has been done, you’ll be able to sign in with the new password you’ve set up.
Let me know if this fixes your problem.
I tray to do that but i canot change password
https://s18.postimg.org/4zw5ld28p/Capture1122.png
i constantly receives a message that old pass is not correct.
Are you entering the temporary password sent to you as the old password ???
When i click on Reset Password i recive fom avast on my mail message that my pass i reset and link to creata new password
when i click on that link i get option to create my pass. when i do that system automatically log me on myavast. When i tray on my avast
change password i recive meeesge that old pass is not correct and and not allowed me to change pass.
I am 1000% sure that i entering good password in field old pass but system says that old pass is not correct.
Thanks for your help, I give up for now.
time to go on work.
Contact Avast:
http://support.avast.com/support/tickets/new