I have exactly same issue with the access to authentication page on SAP.com. With the option “Enable HTTPS scanning” enabled I am unable to login using SAP SID. Sample:

Entering URL: https://launchpad.support.sap.com/
I am forwarded to: https://authn.hana.ondemand.com/saml2/sp/mds
Ending with: https://accounts.sap.com/saml2/idp/sso/accounts.sap.com - No page available

With “Enable HTTPS scanning” disabled - everything is OK!

I tried to add exceptions for sites and scenarios:
.hana.ondemand.com/
.sap.com/
But no luck!

May be I have to use different format for exceptions?
Like:
https://.sap.com/
?

P.S.
Tested:
https://.sap.com/
https://.hana.ondemand.com/
Same negative result!

P.P.S.
I am using the latest free version: 17.3.2291
I had no issues on the previous Avast versions to access SAP!