That's weird that it didn't help.
If you could look for the setup log here:
c:\Users\<username>\AppData\Local\Temp\ we could find out why the reinstallation didn't work for you.
Cleanup setup log file name is something like this one:
Setup Log 2018-01-03 #001.txtRegarding the renewal you should have a confirmation email with a subject like
Avast - Order Confirmation (Order #XXXXXXXX) in this email you have two important information
Order ID and
Password.
You can use these two to login here:
http://www.avast.com/en-us/find-order where you can manage your subscription.
If you didn't get the email for some reason, please contact our support directly here:
http://support.avast.com/ and they should help you to get it done.
Thank you.