Fingers crossed it's just dust.
When the laser reads the disc it has to penetrate the clear lacquer coat on the disc to reach the silvered layer that contains the data. For a single layer disc the lacquer coat is 0.6mm thick give or take a few microns for manufacturing tolerances. For dual layer discs it is thicker. Dual layer discs have a higher capacity but require the laser to focus to a different depth to read the second layer. As you can probably tell, there's a lot going on when the disc is being read.
There are a few things that will stop a disc being read properly such as fingerprint smudges and scratches. They're easy to spot though as they're issues with the disc. What's harder to gauge is the dust build-up on the laser lens itself. This also affects the way the player reads the discs. If you open the DVD drawer and notice dust on the surface where you put the disc then you can imagine that the same thickness also now coats the laser lens.
There are cleaning discs that have a tiny brush that sweeps over the lens to remove some of the dust.
What if it's not dust?
You've already ruled out a faulty disc because it plays in the console. What we're looking at then is the inability of the laser to read the disc or of the DVD drive motor to spin the disc up to speed properly.
When the disc isn't spinning properly you can generally feel that because there's little or no vibration from the player as the disc loads. For laser read errors you'll find that CDs will play but some- and then all- DVDs won't. This is because the laser has to work harder to read DVDs than CDs. If it's not putting out enough power to penetrate the surface lacquer then the disc won't read.
Both of the above can only be fixed by replacing faulty or failing parts. These aren't issues that can be fixed by pressing buttons or switching off at the mains. Something is in the process of breaking down and you're seeing the early warning signs.
Laser failure is the most common fault with all-in-one home cinema kits. The lasers themselves do have a finite life span. What I see from the trade perspective is that the lasers fitted to home cinema kits seem to have a shorter life than those in stand-alone players. This could be where some of the cost savings have been made.
Try a cleaning disc first. They're £2-£3 from Ebay or under a fiver from PC World LINK