@andrew.c, I have had best experiences when all necessary files needed to flash a Custom ROM are stored on a microSD card and loaded from there.
Before you try again, check if the model of your Galaxy S9 is one of the devices supported by /e/ OS Samsung Galaxy S9 - " starlte" : SM-G960 F / F/DS / N (Exynos).
These S9 models are not compatible:
SM-G960 0/DS (Snapdragon) Dual-sim
SM-G960 U (Snapdragon) USA
SM-G960 W (Snapdragon) Canada