I've been undermining for almost 4 days with a Core2 Duo and to this day I do not have a single ONIX drive in my wallet, and that I'm using the difficulty: 0.002.
Attached is a catch where I only see 22 miners mining and with few positive results (mine is one of 28.63 KH). Is it so much the difficulty of mining?
Imagen:
https://ibb.co/i2cQg5Are you seriously mining Onix with a CPU?

That is a very bad idea. Mining Onix (or any other X11 algorithm coin) even with GPU's is a very bad idea. X11 coins are in the domain of ASIC miners and mining X11 coins with CPU/GPU is horrendously unprofitable, you'll just waste your time, electricity and money.
If you want to use your CPU(s) to mine, mine a coin that can be mined with CPU's only.