Use ～ずじまい when reporting that something you intended or were expected to do never actually happened — the plan simply fizzled out. It carries a clear tone of regret or resignation on the speaker's part, so it suits after-the-fact reports and postmortems rather than neutral descriptions. It attaches only to verbs, and is common in written accounts and business narration; for a plain statement of fact, ～なかった is more appropriate.