Looking at your guitar from the side can sometimes reveal whether the bridge is the problem.
Usually, when a guitar or other stringed instrument ceases to make a sound when your fingers are in higher positions, it is a result of the bridge being too low. This can also result in a buzzing sound, rather than the string simply going dead. If you have moved your instrument into a drier climate, or if the weather has changed lately, the wood of the top of the instrument contracts and sinks down to a lower level. This causes the strings to hit the end of the fingerboard when you press down on them, and the angle of the fingerboard causes the higher strings to be disproportionately affected. Being in a higher position, such as above the 12th fret, also has an effect, because you are pressing down on the string closer to the trouble area at the end of the fingerboard.
Instructions
1. Unwind the strings enough so that you can remove the bridge. The bridge is just held in place by the tension of the strings, so this should not be too difficult. You may find it easier to leave the strings wound around the pegs but loose, rather than taking them entirely off the pegs.
2. Remove the old bridge and slip the new, taller bridge into place.
3. Tighten the strings back to their normal tension. As you do so, keep a hand on the bridge and make sure it stays straight in all directions. Having a tilted or skewed bridge can also cause the strings to go dead, so take care not to introduce this new problem in place of the old problem. Make sure the strings fit into the grooves on the bridge as you tighten them.
4. Tune your guitar and attempt to play the high E string above the 12th fret again. If it still goes dead, your problem is more complex than you can expect to fix on your own, so seek a professional luthier for help with repairs.
