This URL is working. I tried this REST API using an external REST client and successfully got the response.
Below is the request which is being sent.
POST /services/srest/restserver/v1.0/jsonsdk/SiteAccountManagement/getAllSiteAccounts HTTP/1.1 Host: rest.developer.yodlee.com Cache-Control: no-cache Content-Type: application/x-www-form-urlencoded
cobSessionToken=xxxxxxxxxxxxx&userSessionToken=xxxxxxxxxxxxxxxxxx
Can you test this again.