Edge 1040 dead to the world?

After months of not venturing outside on ye olde bike, I plugged my 1040 solar in to charge up. It was fine when I plugged it in and showed as charging. Left it plugged in overnight. Checked it in the morning. Dead as a doornail. I've tried long pressing the power button with it both unplugged and plugged in. It's still dead. Any suggestions?