I too have just started the Devnet enterprise sandbox and although it sent me the messages that the sandbox was being set up, and that the sandbox was complete, I have never received the message regarding the login/VPN details at all. I do note that the setup script has the following error. I guess this sandbox is still not functional.
setup_meraki_ent' resource command on 'Meraki Ent 3' failed with 'Script runner exited with exit code: 1' error
Error: Script runner exited with exit code: 1
Description: https://api.meraki.com/api/v0/organizations/549236/networks
GET calling: https://api.meraki.com/api/v0/organizations/549236/networks
https://api.meraki.com/api/v0/organizations/549236/networks called successfully
GET calling: https://api.meraki.com/api/v0/organizations/549236/admins
https://api.meraki.com/api/v0/organizations/549236/admins called successfully
No meraki networks available