Like sthegreat2 said, the mining world is reset every 1-2 months. In the meantime, I suggest you try mining at different levels. From my experience, a majority of the mining is done at levels 11-12 and there's huge voids there so digging below that is better. In addition, in those large voids are usually untouched coal/iron/redstone/etc. that you can pick up so it's not like you can't make money either way. Yes, it's more difficult to mine that if you had a fresh map but no, it's not impossible to mine. I hope you have better luck mining! Feel free to pm me if you want any more tips.
