As the subject says, plugins that are very much in my vst bank are showing as missing when I open an old file. Here are the screenshots of the error message when opening and the synth rack which shows the plugins as greyed (except TTS-1 which works) :
Could anyone fathom why this could be happening ? The project was initially created on an older Sonar version, X1 I think

I could of course insert new instances of the synths and route the midi files to them, but that would mean I have lost all the synth settings that should be saved with the project.