Hi! You've probably followed a link from a Microsoft website, such as cdx.transform.microsoft.com, or had a link shared directly with you.
This cloud portal is used by 3Sharp's customer's to manage and share their demo materials. Those individual customer sites are only accessible by invite.
However, the content that is shared can be made publicly available, and that was probably the intention in this case. You can try getting in contact with the person, or website support, where you got the link.
If you submit a support ticket here, please include the link and the name of the demo, and we can try to reach out to the owner and confirm the the sharing permissions are set up correctly.