Cannot completely uninstall AVAST free. Cannot install new version.

I goofed up somewhere. I thought I had uninstalled the app so I could install newer version.
When I tried to install new version it complains that the old version is still installed.
I manually located all the entries related to AVAST and deleted them.
No joy.
Is there a “cleanup” app available that removes all trace of AVAST so I can install the latest version?
MAC OSX 10.13
Thanks.

Presumably the first installation was on a MAC ?

If so you would be best to post this in the Avast Mac Security sub-forum.
https://forum.avast.com/index.php?board=5.0