my Mac (Catalina 10.15) unfortunately does not support Plecs 4.9.2. I would appreciate if you could share a link for the c2000 support package for Plecs 4.8?
I believe your Mac should support PLECS 4.9. Are you experiencing any errors? Are you using Intel or Apple Silcon? There are separate download links for each version.
Regarding the 1.8 downloads, you can access it with this link.