In the context of getting onto an elevated highway, I've heard a misunderstanding between two native speakers about the phrase 我上不去.
For one of the speakers, the phrase meant an impossibility: the subject had tried and failed to get on, or at least it was clearly impossible to get on the highway.
For the other, the phrase just meant that the subject would not get on, but didn't imply impossibility. The reason for not going might have been because it was impossible, or it might just have been that the subject didn't want to go.
Which is the correct meaning? Is there regional variation in this respect?