As far as I can tell, this extension is irreparably broken.

My previous experience with OneTab had been fantastic! I was able to cache tabs I wanted to keep and come back to them later, even name and organize groups of tabs based on personal categories. It was great! But sometime in the past few months, the extension no longer loads properly: when I open the tab list, it shows a line of pulsing dots indicating that it's loading...but it never loads, no matter how long I wait for it.

I've tried closing and re-opening Firefox, shutting down and restarting my computer, disabling and re-enabling OneTab, disabling every other extension I have, even removing and reinstalling the extension, and nothing changes this lack of response. After losing every tab I had open because I accidentally hit the OneTab button and sent all of them to a window I can no longer access, I'm finally writing it off as a complete loss.

This was previously a great extension, and I hope that someday it will be again. But until then, I'm sad to say that it's not what it promises.