Need Help From Avast

Full system scan shows no progress - hung up on zero progress. Have Avast message that says license is corrupt. How do I contact Avast for assistance?
Thanks

have you tried avast repair?

controlpanel > ad/remove programs > avast > uninstall/change > repair option

you have of course removed previous used AV and used that vendors removal tool
General: Uninstalling a third-party antivirus software https://www.avast.com/en-eu/faq.php?article=AVKB11#artTitle

avast support https://support.avast.co > submit a support ticket

This is your best course, right here on the support forums.

Though this topic should go in the Avast Free/Pro/Premier forum - https://forum.avast.com/index.php?board=2.0.

First try these options and if not resolved start a new topic on the forum mentioned above.
Try a repair of avast as mentioned.

Resend avast License http://www.avast.com/resend-license-paid.php, you will need to enter the email that you used when purchasing the license, e.g. the one that the original email with the link was sent.