The situation where a promising idea / proposal / project either dies or is in development far too long and thus emerges too late, missing its moment, because of excessive amendment-and-approval requirements.
"Imprisoned in the elevator" is usually a product of:
(a) there being too many people in the organization whose sole purpose seems to be to wander around finding pies to put their fingers in but who add nothing to the "recipe" even though they can force others to make changes; or
(b) mandated internal processes which mandate that the approvals process be repeated for every change to the project, however minor; or
(c) managerial timidity, because moving something up and down is easier than risking one's neck with a firm yes or no.
Result: a viable or even great idea doesn't make it out the door on time or at all because it keeps repeatedly moving up and down the approval levels as each change has to be reviewed, re-reviewed and approved and re-approved The project stays in the building because it has been imprisoned in the elevator, never getting out, just forced to go up and down.
"Hey, did your online information project get done, Dan???"
"Nope. It's imprisoned in the elevator."