Same here. But TWO units failed within about three years of purchase.
One I put into service immediately, and left it out on site, powering a few things, including a water pump on a timer. I have no idea how long it lasted, but it obviously failed sometime within that three years, probably sometime in year two as I noticed the water tanks we’re not staying full. The other one I just pulled out of storage, after never having used it. GoalZero claims that these things, “maintain a full charge for up to 14 months,” so it should’ve maintained enough capacity to not destroy the batteries. Apparently it did not.
MY SOLUTION TO RESTORE CHARGEABILITY:
After multiple resest, holding down the units/light/Info buttons, while also unplugging plugging the “input“ charge plug, and listening to multiple BEEP BEEP BEEP… I finally hit upon just the right combination of power cycling and button holding. The display is now at least showing 47 W input, and staying on.
Meanwhile, my 2kWh LiOn system powered right up, and charged from 0 to 100% within four hours (IN MIDWINTER AFTERNOON LIGHT!) after sitting idle for even longer than the goal zero junk. YMMV
After this experience, I’m much more interested in finding a power storage option that doesn’t depend upon limited lifetime equipment. Maybe a few super capacitors for momentary slumps in power generation, and just use power when the sun is actually out. ¯\_(ツ)_/¯
I do like this idea of hot sand tank storage. I’m pretty sure that sound doesn’t have a “charge cycle” in the mere hundreds!

Do we have a thread about that?