You get a launch error when there is missing or incorrect data in the launch that is sent from the Learning Management System / Platform.
Detail: This tool did not receive a proper launch and there either was no tool session from a prior launch. If this is the initial lauch, the LMS probably sent broken data. If you have been using the tool for a while, it may have lost its session due to a bug in the tool. If is the first time your are testing the tool you may have omitted the trailing slash on the launch URL.
One of the first things to check is to make sure that both the tool and LMS / platform are officially certified at https://www.imsglobal.org/cc/statuschart.cfm