Open Telegram.
Go to Settings > Data and Storage > Storage Usage.
Tap "Clear Telegram Cache".
Manually Sync Contacts (Android Specific):
Some Android devices have a system-level option to force a sync.
Go to your phone's Settings > Accounts (or Users & accounts).
Find and tap on Telegram.
Tap Account sync (or Sync account ).
Ensure "Contacts" sync is enabled, and you telegram number database might see an option like "Sync now" or a three-dot menu to trigger a manual sync.
Log Out and Log Back In (Last Resort):
This is a more drastic step and will require you to re-verify your account. Make sure you can receive the login code (SMS, in-app, call, Fragment) before doing this.
Go to Settings > Devices (or Settings > Privacy and Security > Active Sessions).
Restart the app and log back in using your phone number and the verification code.
Add Contacts Manually:
If only a few specific contacts aren't showing, you can try adding them manually.
Open Telegram.
Tap the New Message icon.
Tap "New Contact" (or "Add Contact").
Enter their name and phone number (ensure the correct country code).
If they are on Telegram, they should now appear in your list.
Check for Server-Side Issues:
In rare cases, there might be temporary issues with Telegram's servers. This is usually resolved on its own. You can check websites like DownDetector or Telegram's official support channels for widespread outages.