avonex problems

hello guys!i m Delia,i am 15 years old and i have ms since may 2022.I am on avonex from september 2022 and recently i found some problems on my pens.They work good until I want to set them off,the blue button is so hard to push. I tried to push the button using my both hands, and still it did not trigger. Have you experienced this?Do you know some tips?