Assuming that you have the correct cap, I'd take a look at the rotor itself. Make sure that it is seated correctly. If that's good, place a straight edge across the old cap and measure down to the button. Do the same to the new cap. Also check the inside dimensions of both caps and make sure that the line up notches are in the same position as the old cap. One last thing, make sure that the rotor cap button isn't stuck. This also would prevent it's fitting.
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Hi,
Assuming that you have the correct cap, I'd take a look at the rotor itself. Make sure that it is seated correctly. If that's good, place a straight edge across the old cap and measure down to the button. Do the same to the new cap. Also check the inside dimensions of both caps and make sure that the line up notches are in the same position as the old cap. One last thing, make sure that the rotor cap button isn't stuck. This also would prevent it's fitting.
Best regards, --W/D--