You can go to craftedge.com and download the latest version of the SCAL software. I am guessing you have not updated your software in a while. The site says SCAL is MAC compatible from OSX 10.6-10.12. I don't know where High Sierra falls in that range. If you have issues you can contact Brandon, the software developer directly at
info@craftedge.com. Please let us know the results either way. Thanks.
The latest version is 4.069