Hello Nedim,
I cleared the cache on my browser after restarting IIS on the server. At this point I have the two sites set to use the centralized store and SNI. One site payment.mpcer.nau.edu is working. I can connect and it shows as a secure connection. However the other site cawl.nau.edu is not working. I cannot connect to it using SSL, but my non-ssl binding is working (http://cawl.nau.edu).. I'm using the naming convention suggested in the article where my certificates have the exact same spelling as the domain names (i.e. cawl.nau.edu.pfx) and the certificates in the store look good (names are the same and all of the attributes now show up). It seems like IIS isn't finding the certificate for cawl.nau.edu..
cheers, Paul