In AM 5.5 SSO token validation no longer functions and returns a HTTP 500 Internal Server Error error.
The following getSessionInfo call work fine in AM 5.1.1/5.1/5.0 but no longer function in AM 5.5.
Result in AM 5.5:
Furthermore the API Explorer also returns an Internal Server Error, as does a request where tokenId is included in the POST body.
Note if API version 2.0 is specified the call functions as expected: