There’s an ongoing issue with Cornerstone and the Comet Cache caching plugin. The exact issue has been described before here: https://theme.co/apex/forum/t/compatibility-between-cornerstone-and-comet-cache/14013
TLDR: When Comet Cache is enabled, Cornerstone is not loading. It affects both X and Pro. URI exclusions as proposed in the aforementioned thread do not resolve this issue. Console Error log:
For reference, these issues have been created on Comet Cache’s Github: