Error - LoginContext key cookie was not present in request

[Rod Widdowson]

..and you do have the metadata for this SP loaded?  I'm not hugely
experienced with the failure characteristics of V2 but this doesn't feel
like the error I would expect.  Also the way I'd go about troubleshooting
this myself is not how most people would...

Also, in case you haven't already, have you reviewed
https://wiki.shibboleth.net/confluence/display/SHIB2/IdPTroubleshootingCommo
nErrors ?