Older Aura SSD don’t have the needed firmware on them to work correctly [https://blog.macsales.com/42466-a-note-on-high-sierra-compatibility-with-third-party-ssds|A Note on High Sierra Compatibility with Third Party SSD's] This SSD was sitting on the shelf awhile.
Here’s the needed update to get your drive going: [https://eshop.macsales.com/Service/Knowledgebase/Article/26/730/Aura-SSDs-Firmware-Update-beta|Aura SSDs: Firmware Update]
Once it’s working a second update will happen when you install High Sierra directly onto the SSD.