This information is insufficient to determine what went wrong in your implementation for a single logout. Could you provide the following information.
1) Okta single output settings, which can be found in SAML settings → Advanced settings on the General tab of your application?

2) , Okta?
3) SAML ? ?
. SLO .
<samlp:LogoutRequest xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion"
ID="_d2be8c5de3aeeeac27c8xxxxyyyy"
Version="2.0"
IssueInstant="2016-04-27T16:15:06Z"
Destination="https://org-name.okta.com/app/simplesamlphpexample/exk4xxyyPcvdVq70x7/slo/saml"
>
<saml:Issuer>http://localhost:8888/simplesamlphp/www/module.php/saml/sp/metadata.php/example-okta-com</saml:Issuer>
<ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
<ds:SignedInfo>
<ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
<ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
<ds:Reference URI="#_d1be8c5dc2aeeeac27c8daf04b7xxxyyy6b36287bd6">
<ds:Transforms>
<ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />
<ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
</ds:Transforms>
<ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
<ds:DigestValue>{{some_value}}</ds:DigestValue>
</ds:Reference>
</ds:SignedInfo>
<ds:SignatureValue>{{some_value}}</ds:SignatureValue>
<ds:KeyInfo>
<ds:X509Data>
<ds:X509Certificate>{{some_value}}</ds:X509Certificate>
</ds:X509Data>
</ds:KeyInfo>
</ds:Signature>
<saml:NameID Format="urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified">{{email}}</saml:NameID>
<samlp:SessionIndex>{{some_value}}</samlp:SessionIndex>
SLO .
1) CanonicalizationMethod http://www.w3.org/2001/10/xml-exc-c14n#. http://www.w3.org/TR/2001/REC-xml-c14n-20010315.
2) - "CDA_Main\hjami". , Okta ? , , Okta ( → ). , userName Okta login/email .

( CDA_Main\hjami) Okta , , , .