I recently had the same problem with my minitek unit: I can’t get the unit to turn on. I tried leaving it plugged in for two days to see if it would charge, hopefully fix itself.
The unit won’t turn on regardless of how long I hold the power button down and when I plug in the usb power to charge, the light next to the power button flashes green. The user manual says nothing about being off and flashing green.
Like the post @holabar above I put a paperclip into the reset hole on the side and it works again. Plugged in the unit and now the light next to the power button is red like it should be. Turned on the minitek and it is working again.
Yesterday I tried taking the unit apart but that didn’t yield any results other than breaking one of the clips on the inside and discovering that 4-5 years of daily use makes the inside very dirty. Before I found this post I was thinking that perhaps the battery in the unit has gone bad. I didn’t see any disassembly videos on youtube of someone else who may have braved to crack their minitek open.
Thank you @holabar