Two credentials, not interchangeable. cvk_… = the shared fleet key baked into every APK — it can enroll a device but cannot read any audio. cvd_… = the per-device token issued by POST /ptt/enroll — this is what reads clips.  ·  Retention: clips age out after the window (default 24 h) — a 404 on audio means aged out, which is normal. Telegram remains the permanent archive.