If I have a reed that will not play for me, I have a set of steps that I will take. Many reed problems can be fixed by sanding the back of the reed to make sure it is flat.
Your mouthpiece table should be flat, and the back of the reed should also be flat. If you take your reed and lay it down on a very flat surface, such as a piece of glass, you can gently rock the reed back and forth and see if it is flat. My favorite way to check, is to take the reed, lay it on the flat surface, put even pressure on the entire reed with my fingers, and rub it around in a circular motion on a clean piece of paper. Do this for about 30 seconds, then pick up the reed and look at the back. You will see that some parts of the reed are shiny and some are not. The shinny parts are high spots, and the dull parts are low spots.
The idea is to make all of the back shiny. I like to use a piece of extra fine sandpaper, usually around 400 grit. The sandpaper is Grey in color. Take the sandpaper and lay it down on a very flat, clean surface. Now position the reed so that you are sanding the back half of the reed. You DO NOT want to sand all of the back of the reed, this will take wood out of the heart and the tip and make your reed too soft. I like to use side to side motion. It is important that you don’t send in just one place and create a line where you sanded. Go side to side about 10 times, and then rub the reed on some paper (or the back of the sandpaper) and check to see if there are dull looking spots (low spots). You want to sand until the low spots are gone, and all of the back is shiny.
We only want the back half of the reed to be shiny. Most of the front half doesn’t even touch the mouthpiece. Put the reed back on your mouthpiece and try it out. It will probably play better. I sand the back of all reeds. I usually wait until I have played the reed a couple of times, before I do any work on it.