What Spawner are you using, and is $PATH in a terminal?
Generally this means you need to set the PATH environment, and how will depend on which Spawner you use. If it’s a container, this is usually
You can always use Spawner.environment, but this isn’t very nice for PATH since you have to explicitly set the full path, and can’t do simple additions like PATH=/something/bin:$PATH
I often like to use a launch script that does things like activate environments, source profile files, etc. so that PATHs are what you expect from a typical shell session.