Sorry everyone if I have not been able to address your account in the past 2 weeks. I have been working on organizing the upgrade of the sandbox to 15.4.
The upgrade will occur at the end of March, followed by 1-2 weeks of configuration. As I do not work for CA, I administer the box on my own time so I hope to have it configured within the first week, but life can sometimes get in the way of volunteering.
This is a new install, so all accounts will be wiped along with all data and work you have done to date. Since this is a sandbox and the agreement that this is not to be used for commercial purposes, there should be no issues.
Once the system is back up, you will have to request new accounts. This also works well to clean up old, stale accounts.
Thank you for your patience,