No Mobs Spawning

I am currently in a world that is locked in hard mode but no mobs are spawning naturally in the overworld whatsoever. The only mobs that do spawn are in the nether, from spawners, and phantoms (I haven't checked the end because I haven't been there yet) I have also been noticing a decline in passive mobs, but that may be just due to low spawns rather than the bug. I uninstalled and reloaded a save of my world as well, but it still isn't working for me. Is there anything you can help me with regarding the issue?