I assume you have completed the course and unfortunately the cloud-based environment does not persist once you complete the course. We do this to conserve resources used by our cloud instances. For this reason we have made VM images available for download in the course's "Completing the Exercises" lesson.
Hi, thank you for confirming your information for us. According to our records, you completed the course on 4/18/19. Once you visit a lesson in a course, then navigate away from it, it is marked with a green checkmark in the Course Overview to indicate it is complete. I believe what unfortunately happened is that just by visiting the Solution Build lesson, then navigating away from it, our system marked you as having completed the course, even though you had not completed running through the solution build, and your exercise system was deleted. If you instead install the VM we provide (in the Completing the course exercises section), you can complete the solution build at your leisure, without worrying about losing your work again. Sorry about that!