Iray crashes

Hi Im fairly new to Substance 3D Painter. I have been using it for over 2 months now. I was importing textures and rendering with Iray without anmy issues. About a week ago I was about to open older projects I worked on and suddenly I could not use Iray anymore. When I was previous was able to render other projects now whenever I hit the Iray button it automatically crashes and shuts down the app. Anyone having the same issue ? Would be good to know what has changed. Francois