For the machine not homing:
Make sure you’ve sent the machine configuration per the assembly instructions for your machine: https://docs.carbide3d.com/assembly/shapeoko/#assemble-machine and that the configuration matches your machine and its accessories. Configuring a machine using Carbide Motion 5 and for 517 and later: Setting Grbl Configuration in CM 517 and later or see the ~14 min. mark of this video: https://www.youtube.com/watch?v=krwt3C9aSTY — Note that it may help to temporarily disable or disconnect accessories when troubleshooting.
There is a basic page on troubleshooting the homing switches at: https://docs.carbide3d.com/software-faq/home-switch-troubleshooting/
There is also a Carbide 3D Answer video: https://www.youtube.com/watch?v=P7lOLMAcl_0&feature=youtu.be
For the new inductive homing switches:
Troubleshooting: https://www.youtube.com/watch?v=Zf8NPmxrEDs
and Adjusting: https://www.youtube.com/watch?v=EZDBza_B25Q