Can't say for sure without looking at the reel, but the leading cause of stuck buttons is salt water intrusion. Chances are that the spring that pushes the button back out isn't powerful enough to overcome the added friction caused by the salt crystals that formed inside of your reel.
FishCarpiser is right. It takes only takes a short time to rip it apart and clean and put back. I had this problem on one of my internationals and finally I just put a new spring in.
Get the jet lube in a syringe... I used it all the time and it works.. syringe it into there and try to work it out.. if not dont worry about it the lever shouldnt move at all without it.
It has been my experience that the plastic insert that the button rides in gets loaded with salt.On an older reel it is usually brittle and will break while pressing it out to clean it.
However it is inexpensive and easy to replace. Clean the button and lube it with Penn protect or Reel-X before reassembly.
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