b4 and c5 dont play sound

I have a clarinet to which after checking all the keys and springs, it still has a problem, the notes b4 and c5 do not sound, all the others are perfect, do you have any suggestions?
 
Are you sure you mean B4 and C5? B5 and C5 would make more sense. Can you describe the fingering for the failing notes, or where they are on the instrument? If it is B5 and C5 then you probably have a leak on one of the large pads near the bell. This can be a matter of adjustment or it can be a misaligned pad cup.
 
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