It can't be opened probably due to being locked up.
(I deleted your previous post. Please do not multipost.)
Ooops. Even the warning is the same.
Mike-san's translation is more appropriate. If the speaker is trying to open it, there is not any significant difference between the two translations. However, the original sentence can be used also when the speaker is watching someone else is trying it. My one is more likely for 鍵がかかっているみたいで開かない.