How come my honda dirt bike wont shift!?!?!?

I was riding my honda crf 450 earlier 2day, and it wouldn't shift/ gear up 2 4th gear! I just got it back from the motorcycle shop yesterday, and they said everything is fine! And it wouldn't shift up and I am worried about it because I have a competition tomorrow. What should I do? I don't want to drop out bcuz i am not that type of person. What would you do? I need as much help as possible!

it could be the clutch.... its not hard to shift a dirtbike without clutch but you mite no be used to having to shift hard. Check that the clutch engages and disengages. sometimes gearboxes get stuck here and there, keep trying and it could get working

my 450 did that, it got stuck in first gear , i just kept flooring it letting off and trying to shift it, after a few times of doing that it shifted again. But like 2 rides later, i was kicking it over and the case broke. Maybe your bike has a defect also. Honda fixed it for me.

take the bike out for a good ride, even if its a warm up...for now change your oil. make sure you let go of the revs and put the clutch in...i might sound dumb..ur riding a 450 I'm guessing u know how to ride, just change you oils i guess:S

maybe u dont know how to ride...... if thats not it then maybe ur just not pushing up hard enough on the shifter. or ur not getting high enough revs or the people at the shop are just dumb. im just throwing ideas out there cuz ive never had this problem

Clutch maybe? Clutch plates probably. Thats weird. I've never heard this before. Or transmission.

You can force a bike to change gears without holding in the clutch lever... Of course, that is REALLY bad for your bike. I'm just saying it's an option.

im not familiar with how the 450 shift works, are you positive you were able to shift it before?
what else did they say, just "naw its cool"?