I'm a collaborator on a project but I can't start a workspace.

If you are a collaborator on a project and have tried to unsuccessfully start a workspace and the following error popped up in a red toaster box...

"Workspace could not be started. environment 5a74c9af0634dd1b1c9fbce1 not valid or unauthorized"

This means you do not have appropriate access to the Compute Environment (CE) that your workspace is trying to use.  In the screenshot above the error references the ID of the environment, 5a74c9af0634dd1b1c9fbce1. 

Compute Environments can have a variety of different access methods, they can be globally available, or privately owned by a user or an organization.  In the case where you see this error several solutions are possible...

1. You can create or use an existing org and give ownership of the CE to that org and then make sure all project collaborators are in the org.
2. The owner of the CE can make it globally available, although some deployments may restrict wide use of global environments.
3. You can duplicate the CE and basically have your own private copy to use in the project, although this means that any changes to the original CE will not propagate to yours.