Windows 10 Security Update Extension Loading Error

Thanks — that screenshot helps. That "Enroll in Extended Security Updates" dialog stuck on the spinning “Just a moment…” usually means the Settings UI can’t complete the enrollment step (network, account/permission, or a local/service problem). Let’s try a few targeted troubleshooting steps so we can narrow the cause.
Before we start: can you tell me
  • which Windows edition and exact build (run winver and paste the result),
  • whether the PC is domain-joined / managed by your company, and
  • how you started the enrollment (Settings > Update & Security > …, or a script, or a portal)?
If you prefer, try the quick checklist first — otherwise follow the numbered steps below.
Quick checklist (try these first)
  1. Wait 3–5 minutes then click the X and re-open Settings (sometimes it eventually completes).
  2. Reboot the PC and try enrolling again.
  3. Confirm you’re signed in with an account that has Administrator rights and (if required) the same Microsoft account that’s enrolled with your organization.
  4. Temporarily disable any VPN, proxy, or third-party firewall/AV and try again.
  5. Test Internet access in a browser (load Microsoft – AI, Cloud, Productivity, Computing, Gaming & Apps). If that fails, fix network first.
If the quick checklist didn’t help — full troubleshooting steps
1) Restart Windows update-related services (safe & common)
  • Open an elevated Command Prompt (run as Admin) and run:
    • net stop wuauserv
    • net stop bits
    • net stop cryptsvc
    • rename C:\Windows\SoftwareDistribution SoftwareDistribution.old
    • rename C:\Windows\System32\catroot2 catroot2.old
    • net start cryptsvc
    • net start bits
    • net start wuauserv
  • Then restart the PC and try the enrollment again.
2) Run the built‑in troubleshooters
  • Settings > Update & Security > Troubleshoot > Additional troubleshooters: run “Windows Update” troubleshooter.
  • Also run “Internet Connections” troubleshooter if available.
3) Repair system image and system files
  • In an elevated command prompt or PowerShell run:
    • DISM /Online /Cleanup-Image /RestoreHealth
    • sfc /scannow
  • Reboot after they complete and retry.
4) Check account/permissions & sign-in
  • Make sure you are signed into Windows with the correct Microsoft account if the enrollment requires it (or with a domain account that has permission).
  • If this is a corporate device, your organization may require the action be performed through Intune or by IT — check with them.
5) Try a different UI path / alternate machine
  • If you started enrollment from Settings, try signing into the organization portal (or admin center) if your org provided one.
  • Try enrolling from a different machine (same network/account) to see if it’s device specific.
6) Collect the Windows Update logs for diagnosis
  • Open an elevated PowerShell and run: Get-WindowsUpdateLog -LogPath C:\Temp\WindowsUpdate.log
  • Attach that log here (or paste the last 100 lines) and check Event Viewer:
    • Event Viewer > Applications and Services Logs > Microsoft > Windows > WindowsUpdateClient (and also check System and Application for related errors). Share any error IDs or codes you see.
7) If you see a persistent UI hang only in Settings
  • Try creating a new local Administrator account and test the enrollment there (this rules out a user profile corruption).
  • Try the enrollment while booted to Safe Mode with Networking (if your org allows it).
8) If you must apply ESU product keys (enterprise/volume licensing)
  • Enrolling ESU sometimes requires a purchased ESU product key and activation via slmgr; if that is your scenario tell me the SKU (Pro/Enterprise/IoT) and I’ll give exact commands and steps. If you are not authorized to do that, ask your IT/License admin.
What I need from you if the above doesn’t fix it
  • The exact text from winver (Windows edition + build).
  • Any error codes from Event Viewer or from the Settings UI (if one appears).
  • The WindowsUpdate.log file (use Get-WindowsUpdateLog as above) or the last 100 lines pasted here.
  • Whether this is a personal PC or a managed/corporate device.
If you want, I can give the exact commands to:
  • Collect and paste relevant Event Viewer entries, and
  • Apply/activate an ESU key (only if you confirm you have one and this is authorized).
Tell me which steps you already tried and paste the winver output — I’ll guide you from there.