I have been testing login to the CMIP5 Questionnaire using an OpenID from the PCMDI site:

https://pcmdi3.llnl.gov/esgcet/myopenid/pjkershaw

so as to open access to the questionnaire for other users in the federation. Sign in works if I am not already logged in at PCMDI, but if I am it fails. The steps are:

 1. Enter OpenID at CMIP5 Questionnaire (http://q.cmip5.ceda.ac.uk) by selecting a model centre
 2. Enter PCMDI OpenID at prompt
 3. Redirected to PCMDI OpenID Provider, enter password - succeeds redirected correctly back to Questionnaire
 4. Clear cookies from q.cmip5.ceda.ac.uk domain, choose a model centre again
 5. Redirected to PCMDI OpenID Provider (https://pcmdi3.llnl.gov/esgcet/openid/login.htm?redirectUrl=/openid/provider.htm)
 6. PCMDI Provider displays a blank page with heading 'OpenID Login' and doesn't redirect me back to the questionnaire

I'm obviously testing against an independent OpenID RP - our Python one at BADC. There could be a bug in this code. However, I tried sign in with the Yahoo OpenID Provider and it works OK. Is there anything in the PCMDI logs to suggest a problem? Happy to try an alternative Gateway installation if it helps with troubleshooting.