Failed to contact the domain server named. Either the server is down or the domain name is incorrect. LDAP server unavailable

I am stuck with a problem. I am trying to connect to Ax2009 using wsdl url in postman. When I tried to access this URL in the browser, I can access it, but through postman, I get an LDAP error. Error: Failed to connect to testing. Cause. Domain server named: ABC could not be contacted. Either the server is down or the domain name is incorrect. The LDAP server is not available.

code:

using (var context = new PrincipalContext(ContextType.Domain,AuthInfo.Domain))

      

        
        
        
      

    

An error occurred on the first line. Please suggest some solution for this problem. Thank you in advance.