Thank you for your response! I was actually reading another article that was talking about increasing the RAM allocation. I've done a lot of testing, and initially, the geofences were failing without any error when I asked this question. But after simplifying the geometry and trying to re-import them again, it actually was able to import several thousand before failing, and the GeoEvent server logs stated that it ran out of memory.
The initial failing without any error messages is what caught me off guard, but I realize that it was probably way too big and complex for it to even try to import any and provide any useful messages.
Thank you!