What's going on

  Out of your 49,225 photos, 49,224 backed up successfully. One single photo is stuck and Snapback keeps retrying it forever.

  Why? When Snapback asked Google for that one photo's download link, Google said "I don't have that photo." This usually means the photo was deleted or moved to trash in
  Google Photos at some point during or after the backup started. Snapback doesn't know that, so it keeps trying.

  The good news: your backup is essentially done. It's one photo out of 49 thousand.

  How to find which photo it is

  1. Go to chrome://extensions in Chrome.
  2. Find Snapback in the list.
  3. Make sure "Developer mode" is ON (toggle top-right of the page).
  4. Under Snapback you'll see a line that says "Inspect views: offscreen.html" — click that link. A new window opens (DevTools).
  5. In that new window, click the "Console" tab at the top.
  6. Copy and paste this whole block into the console, then press Enter:

  const db = await new Promise((res, rej) => {
    const r = indexedDB.open('snapback')
    r.onsuccess = () => res(r.result)
    r.onerror = () => rej(r.error)
  })
  const sid = 'session_1777234021570_ninb4y2'
  const idx = db.transaction('session_items', 'readonly')
    .objectStore('session_items').index('by_session_status')
  const rows = []
  for (const s of ['pending', 'failed']) {
    const r = await new Promise(res => {
      const req = idx.getAll([sid, s])
      req.onsuccess = () => res(req.result)
    })
    rows.push(...r)
  }
  console.table(rows.map(i => ({
    filename: i.filename ?? '(unknown)',
    date: i.timestamp ? new Date(i.timestamp).toLocaleString() : '(unknown)',
    type: i.type,
    mediaId: i.mediaId
  })))

  A small table appears showing the filename and date of the stuck photo.

  What to do with that info

  - If you see a filename and date: open Google Photos, scroll to that date, look for that photo. If it's not there, it was deleted — nothing to fix, the backup is as
  complete as it can be.
  - If you see "(unknown)" for the filename: the photo was likely deleted very early on. Same outcome — nothing to recover.

  How to stop the retrying

  In Snapback's panel, click Stop on the session. The remaining 1 photo can't be recovered (Google no longer has it), so 49,224 of 49,225 is the final result.

  Send me a screenshot of the table if you want help interpreting it.