X50 shuts down after a period of time if it believes the license file is false or missing. Please delete the X50 config file and reactivate the software, if you used online activation the first time I want you to try offline activation this time and vise verca.
You will find the config file by opening the preset manager and pressing the "Preset folder" button, the config file is in the folder that is opened and named TSEX50v2.xml .. Please make sure you are using the license file for version 2.3 and higher. I hope that helps, if not please use the contact form on our website to make a support request