Way to check If McAfee at fault is open security centre and disable first the firewall and check the access then real time scanner (after re-enabling the firewall).
If you see it work post back.
The extender has it an IP I never used one but if it has it should be allowed in the firewall My network connections listing and in the home network settings .
PS we had to alter your logon to remove the rest of your email addy it is not secure to use email addresses as user names. Just remove everything after the @ and password is the same. You will get an official notification about this later on.