GVH fails to respect the “Sign-Out Landing Page URL

[noor moqady]

after adding this code :-

<script type="text/JavaScript">

if (window.innerwidth < 555) {

window.onload = function () {window.location.replace('http://desktop-ba6mu86/Html5Viewer/...virtualdirectory/Resources/Config/Default#');}
} else {
window.onload = function () {window.location.replace('http://desktop-ba6mu86/Geocortex/IdentityServer/account/signin?ReturnUrl=/Geocortex/IdentityServer/issue/wsfed?wa=wsignin1.0&wtrealm=http%3a%2f%2fdesktop-ba6mu86%2fGeocortex%2fEssentials%2fREST%2fsecurity%2fcallback&wctx=urn%3agcx%3aidp%3aSignInCallback%3aSKW-OHPLilz0Kw1JmKbfKIWwAAJDmV1_FyqUKKlpqqnS1AEwAAx1IULid8yvZxB4qyR4DgLWgC&wa=wsignin1.0&wtrealm=http://desktop-ba6mu86/Geocortex/Essentials/REST/security/callback&wctx=urn:gcx:idp:SignInCallback:SKW-OHPLilz0Kw1JmKbfKIWwAAJDmV1_FyqUKKlpqqnS1AEwAAx1IULid8yvZxB4qyR4DgLWgC');}
}
</script>

to ( SignOut.cshtml ) file my site works fine and sign in and out fine, but after the first "sign out" my site get me back to the sign in page so i could put my user name and password to sign to my site again but unfortunately it gave this error " The callback request was not handled. This is likely a problem with your session. "
what might be the issue in the added code ???