Cannot resolve 'twofactor:TwoFactorLogin' to a type definition for element 'ph:LoginHandler'.

[Ryan Suarez]

Trying to setup shib IdP v2.3.8 with duo two factor auth.  I'm getting this error:

19:09:11.757 - ERROR [edu.internet2.middleware.shibboleth.common.config.BaseService:188] - Configuration was not loaded for shibboleth.HandlerManager service, error creating components.  The root cause of this error was: org.xml.sax.SAXParseException: cvc-elt.4.2: Cannot resolve 'twofactor:TwoFactorLogin' to a type definition for element 'ph:LoginHandler'.|

I have this in my handler.xml:
------------
<ph:ProfileHandlerGroup xmlns:ph="urn:mace:shibboleth:2.0:idp:profile-handler"
                     xmlns:twofactor="http://duosecurity.com/2012/shibboleth/idp/twofactor"
                     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                     xsi:schemaLocation="urn:mace:shibboleth:2.0:idp:profile-handler classpath:/schema/shibboleth-2.0-idp-profile-handler.xsd">
…
<!-- DUO -->
   <ph:LoginHandler xsi:type="twofactor:TwoFactorLogin" 
   jaasConfigurationLocation="file:///opt/shibboleth-idp/conf/login.config"
   skey="..." ikey="..." akey="..." host="...">
  

 <ph:AuthenticationMethod>urn:sheridancollege.ca:ac:classes:PasswordProtectedTransport:duo</ph:AuthenticationMethod>
   </ph:LoginHandler>
--------------

I have /opt/shibboleth-idp/lib/twofactor-login-handler-0.2.jar which contains this schema definition:

https://github.com/duosecurity/duo_shibboleth/blob/master/twofactor-login-handler/src/main/resources/schema/shibboleth-2.0-idp-twofactor-login-handler.xsd

Any ideas why I'm getting this error?