This is also happening to me, and yes, also on Windows Insider Preview.
I have tried a bunch of things, uninstalling, reinstalling, deleting registry keys. Nothing works for me.
I even tried installing SSMS 17.9.1 which uses VS 2015 Isolated Shell and get the same error message from that on startup.
2015 Isolated Shell actually shows up in Add/Remove Programs unlike 2017 so I am able to try and repair it from there, but that did not work either. Looks like some sort of incompatibility with the Insider build.