Receiving HTTP 500 error from API call

I'm following the basic steps outlined for API access. I can reproduce using both curl and Postman. With curl, I can successfully obtain a session token using:

curl --data-urlencode username=myname@company.com --data-urlencode password=xyz https://api2.clarizen.com/v2.0/services/authentication/login

However, trying to issue an entityQuery, I get a 500 HTTP error. I'm using:

curl --data-urlencode typeName=Issue --header "Authorization: Session xxxxxx" https://api2.clarizen.com/v2.0/services/data/entityQuery

The response includes:

{"errorCode":"Internal","message":"An internal error has occurred, the error was logged and will be examined.","referenceId":"2fwW2pspLqjGmDzqazQAfH"}