Playback feature may not be available on this Disc

I have a Denon DVD 1815 5-disc DVD player. Today I tried to use it and kept getting the message above. So far the only information I have found on this has been from JustAnswer, where someone wrote

I haven’t really used this piece of equipment heavily. Does the amount you use it have an affect on the laser getting “out of tune”, or is that just a function of age?

Are you getting this error on every disc you put in the player, or only on one disc?

Every disc, and in every tray, although that last is unlikely to be relevant, since it rotates to put the disc over the laser. I’ve tried 5 different discs so far, all of which have played in this machine.

Could also be a dirty lens. In my experience with DVD players, after some years in use, they begin to be not able to play first some, then almost all disks (admittedly, I’m a smoker, so the contamination is most probably higher than usually). I have been able to clean it on different players by disassembling the case, looking for the lens and rubbing it with a cotton swab and alcohol.

Hmmm. I don’t smoke, but I do have two cats, and despite being short hairs, the shed fur is epic. I’ll have to see if there are kits for cleaning lenses without disassembly, since getting the player out of the cabinet is problematical (tight fit and cables all snugged together with cable ties). Worth a shot, I suppose.

dust and dander can get on a lens.

Well, I tried using a DVD cleaner to clean off the lens. No dice. Guess the laser really is busted (either it isn’t focusing right or the head can’t move).

Bugger.