Problems: The folder has a number over 1000 and isn’t synchronising with the iPhone

Try this quick check…
Open the OneDrive app on your iPhone and tap the search icon (magnifying glass). Type the full name of one of the missing folders, like now1002rampf.

• If it shows up in search:
  Great news – the folder is fully synced. You’re just hitting a display quirk where the app doesn’t show every folder while browsing (likely because there are many items in that view). You can always jump to it using search. If you want it to reappear while browsing, try moving some older folders into a subfolder (like “Archive”) on your PC to shorten the list.
• If it does NOT show up in search:
  Then it’s a sync issue. Double-check you’re signed into the same Microsoft account on your phone. Pull down on the file list to refresh, wait a moment, and search again. If it still doesn’t appear, try signing out and back in, or check via the Files app (if you’ve added OneDrive there).

That’s it. Search will tell you immediately whether the folder is safe on the server or genuinely missing. No need to guess why the browse view misbehaves – the symptom is clear, and the workaround is simple.

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Hope this will help you.