Came across a bug after building several AltspaceVR worlds with the same project and occasionally Unity will crash and I noticed since a particular crash I could not apply skyboxes to my templates.
No matter how many times I’ve restarted my client or started a new template the skybox would not apply.
After Googling around I came across a suggestion to toggling and untoggling the skybox visibility even if it is marked as showing. Re-toggling does some sort of reset and in this instance fixed the issue.