La solution semble être dans le fichier "ReadMe_About_ReWire.rtf" (que je n'avais pas lu) qui se trouve : C:\Programmes\MAGIX\Samplitude Pro X7 Suite\Effects\Customize\ReWire.
Contenu du fichier :
ReWire.dll Installation
If you don't have the ReWire.dll installed yet or an older ReWire.dll, please copy the ReWire.dll into the appropriate folder (see below).
For 64 Bit support, you can additionally copy the 64 Bit ReWire.dll (which has the same name, unfortunately).