Cubase 10 install Corrupted Cubase 8.5?

Hi there, hope someone can be of some help,
I Purchased and Installed cubase 10 on my Pc, I already have Cubase 8.5 installed, now when i try to open Cubase 8.5 to work on projects in that version i get error messages to say halion sonic content is missing, also Sylenth1 vst is missing and will not load within cubase 8.5 although within plugin manager it is pointing to the correct folder, also within the plugin information panel in cubase 8.5 there is only the update button within the vst plugins tab, VST 2.xPlug-in Paths and update Plug-in Information is missing??
any ideas? pulling my hair out here!
Thanks in advance for any solutions


Have you installed Cubase 10 from the Full Installer? Is Sylenth1 plug-in up-to-date?