You must disable System Integrity Protection (SIP) on your Mac before Grave can attach
to the Minecraft Java process. macOS blocks unsigned binaries from injecting by default, and Grave is
not Apple-notarized. This is a one-time change made from Recovery Mode.
Your Grave license is HWID-bound to a single device. It activates on the first machine
you use it on, and you cannot run Grave on two systems at the same time.
Exceptions can be made. Open a support ticket and explain why you need access both a macOS and Windows device, an exception may or may not be granted.
macOS also requires SIP (System Integrity Protection) disabled before Grave will run.
See the macOS injection page for how to do that.