Good Morning from Central Oregon. I’m 67 years old and have been playing for about 1 year now. I’ve taken JP’s Happy Harpin and his Blues courses. For some reason I’m still having trouble with the 8 draw note on my C Harmonica. On some occasions I barely get a note out of it. Any suggestions?
My guess is that the gap of the 8 draw reed needs to be adjusted. There are various online tutorials about doing this (youtube videos, where you actually see what to do).
Basically it is quite easy. Remove the covers from the harp and on the bottom side you will notice that the reed plate there has the reeds on the outside. These are all of the draw reeds.
Observe the free end of the reeds, comparing the gaps (distances between the free end of the reed and the end of the reed slot in the reed plate). On the longer reeds (the lower notes) the gaps are the largest. As you progress up to reed 8 you will see that the gaps have progressively narrowed.
Either the gap for reed 8 draw is too large or too small.
If the reed 8 gap appears much greater than you see for reeds 6, 7 or 9 then you should use (for example) a toothpick and carefully press down on the free end of reed 8. Release and observe the gap again. If the gap did not change, you did not press down far enough. Repeat until the gap seems to be smaller than the gap for reed 7, but larger than the gap for reed 9. The differences are very small !! 
If the gap was initially too small or you pressed down too much, there will be no gap left or the free end of reed 8 will be below the surface of the reed plate – bad news, since you will no longer be able to get any sound at all from it. If that happens, use your toothpick (or whatever) and insert it into the hole for reed 8 that you normally draw and blow through and press the reed 8 back up so that you can again see a gap at the free end of reed 8 and above the surface of the reed plate. Continue adjusting the gap and testing the result by playing the harp (drawing through hole 8) until you have an easily playable result. 
As I said, check out youtube videos where the techniques for reed gapping are easier to understand than by just reading about the method.
Regards,
– Slim
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Hey - welcome to the forum! Happy to have you here. What brand harmonica is it, and how old is it? Have you ever rinsed it out with water?
If it’s only happening -8, and not -9 or -10 then it does sound like it’s more likely an issue with the harp and not your technique. All of the advice that @Slim has given you is spot on, if you’re the tinkering type
But lmk the brand and age of the harmonica.
Aloha,
Luke
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