When I set things to render to Vantage and go back to GPU, Cryptomatte stops working. It is in the elements list, but I have to delete it and add it again. I get the warning that Vantage doesn’t support Cryptomatte, but it shouldn’t break it.
You need to re-enable Cryptomatte by toggling on the “VrayVFB” setting for it to work again. Vantage annoyingly disables it and doesn’t re-enable it automatically on unlink. Would be nice if either Vantage just ignores Cryptomatte or at least re-enable it when unlinking. You shouldn’t have to re-enable it manually every time.