Microsoft announce that Dynamics 365 Layout will be discontinued as a separate application and will not be offered to new customers after 1 June, 2020. Current customers will be able to use the application until 31 December, 2021 or when their current subscription ends, whichever is earlier. Core Layout capabilities will be integrated into the Dynamics 365 Guides product.
See the announcement here and suggestions on where to get assistance if you’re an existing customer: https://bit.ly/2YooZ4n.