A Nintendo Switch/PC/Ps4/XBox remake of the 2003 Gameboy Advance games HM: Friends of Mineral Town and HM: More Friends of Mineral Town. [ Game Guide ] JP release = Oct 2019. NA release = Jul 2020. EU release = Jul 2020.
It sounds like you're doing everything right, so you're probably just having some bad luck. You also have to have room to hold it in your bag, but typically if you're mining, you leave room anyway for gems and such.