Hello, thank you for reaching out to Microsoft Q&A.
Several users experienced issues when registering for the ESU program on their Windows 10 PCs. Since higher registration numbers or multiple registrations may be recorded for the ESU program within a short period, you may be having trouble registering successfully right now.
However, in your situation, it is also recommended to check a few things before attempting to register for the ESU program.
- Sign in to your Windows 10 PC with your Microsoft account.
- If you did not receive the verification code on your alternate email, check your Junk or Spam email folders to see if the code ended up there.
If you're unable to find the code, sign in to your account here-
https://account.live.com/proofs/Manage on your web browser.
Then, select 'Add a new way to sign in or verify' > Enter your phone number or use an authenticator app.
Next, enable two-factor authentication on your account.
Once these security changes are made, simply restart your computer and enroll in the ESU program.
Verify your Identity using the new options you added.
Let me know how it goes.