If you face “Error: User does not have access to this service provider” exception, then the Profile doesn’t have access to the Connected App create as part of the Single Sign On.
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In the SAML tracer, you will find “urn:oasis:names:tc:SAML:2.0:status:AuthnFailed”.
You can use SAML Tracer extension and check SAMLStatusMessage and SAMLStatusCode values.