Informational broadcast:
I just made the mistake of updating Illy v.26 to 26.5.2, now double clicking on .ai or .pdf* launches it even though 27.0.1 is running... (Windoze 10)
This is the same old issue I posted about on previous versions and setting a default app does not solve the problem. The solution is to remove 26.5.2 which I'll do as the only plug-in I need - Fine Cut 9 - which is not supported in 27.0.1, does actual work in 27.0.1 - I am so grateful**.
* Yes, I have Illy as my default pdf app, yeah I do.
**Happy Thanksgiving everyone!