I've read the replies and while I agree that saying "FML, Richie left, I'm sooo sad I can't sing" could be an easy out (and the word depression gets thrown around way too much), I'm wary to downplay the importance of his mental state. Jon really looked like shit after Richie left, and he's too bad of an actor when trying to emote. He didn't sing for 2 years after the end of the BWC tour, so how could he lose his voice if there's no physical problem? I find it hard to believe that a professional singer with 30+ years of experience can destroy his voice only because he didn't practice for 2 years. Many other singers have faced worse problems or lost their voices for good and manage to recover (even if it was partially) due to a medical procedure or new technique/working harder. So my logic says there has to be something else.

I think the key is that whatever problems he's having are linked, and that make it worse. It's not only a voice issue, it's a major shock to the order of things (Richie + the breakup with the label), plus learning to sing again to accomodate his new voice, plus deciding whether to continue, getting new people onboard and many other things. He didn't have the best voice to begin with and then all this shit happened. So I can see why it's taking him longer to recover, IF he ever recovers.

Edit: He could be also contributing to his decline by not having a healthy livestyle. He could be smoking again, many people do it when facing a stressful situation, or doing other things that could damage his vocal cords, who knows, I'm not saying he's a poor blameless victim here because we don't know what's happening behind the scenes.