I don't know if that solved your issue, but if you havent done so yet, you have to install the M5 Board Manager in the Arudino IDE board manager settings or M5 units will not appear in the board list.
Go to this page and follow the steps for your operating system: M5 Stack Cardputer How to Article

By the way, I ordered my cardputer today and when it arrives I will create some wall mount models for 3d printing. Watch the projects page. I already have some nice M5Stack wall mounts and travel cases up there. :)