Microsoft are making a number of changes to how trials are provisioned for Dynamics 365 and CDS.
The first change has been announced – please read https://blogs.msdn.microsoft.com/crm/2018/10/05/announcing-changes-to-new-trials-and-new-cds-orgs/
Expect more changes to come
If you are a Microsoft partner you can make use of https://demos.microsoft.com/
