I am having the same issue. My best guess is that OpenCL is now deprecated on macOS 10.15 Catalina and GPU cracking natively will no longer work. I had limited success using the -O option.
source of my speculation:
https://hashcat.net/forum/thread-7554-po...l#pid40657
source of my speculation:
https://hashcat.net/forum/thread-7554-po...l#pid40657