I haven't flown my DJI Mini 2 in about 6 weeks and now it won't power on at all. The battery was fully charged when I put it away. I'm pressing the power button correctly (once, then hold for 3 seconds) but nothing happens - no lights, no sounds.

I've heard about something called hibernation mode? Could this be the issue? The battery doesn't seem damaged or swollen. Any tips on how to wake it up or should I be worried about permanent damage?

Battery details: It's been stored in a cool, dry place in my camera bag. No visible damage to the battery or contacts.

Yes, this sounds like hibernation mode. The battery goes into hibernation if it's been depleted and stored for too long. You need to fully charge the battery to bring it out of hibernation. Try charging it with the original DJI charger for a few hours and see if it comes back to life.

There was actually a known issue with Mini 2 batteries not self-discharging properly if left in the charging hub or drone, which DJI fixed in a firmware update. If you haven't updated your firmware recently, that could be contributing to the problem. After you get it charged and working again, make sure to update everything.

This exact thing happened to me last month! Left my Mini 2 unused for about 2 months and it was completely dead. Had to plug it into the charger for several hours before it showed any signs of life. Now I make sure to charge and discharge my batteries every 3 months like DJI recommends to keep them healthy.