I'm trying to recover some old SONAR projects but I'm not able to load the synhs (however the synths are installed)
 

 

 
 
I liked some presets so I want to recover them. Is there any way to repair the project?

How to fix it?

Have you changed the location of your VSTplugins folder, renamed or moved the folder itself somewhere else by accident?

Have you changed from 32 to x64 sonar?

lawp
Have you changed from 32 to x64 sonar?

I think the VST plugins location is a generic setting used by Cakewalk products, not just application specific, being usually under Cakewalk\VSTplugins, rather than the application itself.
 
Looking at the synth browser linked above, all the synths are missing, which suggests a folder related issue. I might be wrong though :)

Or installed a different format such as VST where the original project used DXi?

I've opened projects started with 32bit plugs into x64-only and some but not all get replaced, depending (I think) on the vstid... And definitely dx plugs won't be automatically replaced by vst versions