I attempting to access the following resource and it is telling me that I do not have access:
How do I acquire access to this resource?
Support will have to help you with access to the link. However, the link goes to a support document on how to set up a local test server. It does not go to any type of Schoology sandbox.
We have a great thread that has addressed possible issues of why users may receive a message that they do not have access to a resource in the community. I recommend checking out the resolutions in this thread.