Did you happen to get ores from any of the rocks, aside from the one that breaks? Sometimes, if you're using a Silver Shovel, you'll get numerous ores instead of money bags from what should be the day's money rock.
If it's not that, I'm not sure. Maybe the rocks, or at least the particular money rocks for the past two days, are surrounded by flowers or something and there's no space for the money bags to generate? Can't know for sure without seeing the rocks, so just a guess.