Not found - POST https://mysite.xyz.com/Shibboleth.sso/SAML2/POST HTTP/1.1

[Mak, Steve]

Uday,

You most likely have a problem in your shib.conf on the SP box for Apache in conf.d.

You need to make sure that mod_shib is loaded and Location /Shibboleth.sso is reachable by everyone.

Apache needs to know to route all Shibboleth.sso calls to the shib module.  If you're getting a 404 that means Apache isn't configured to route it properly.