Cannot network boot with the downloaded image file

Symptom:

Booting from the image specified in the URL fails.

Solution 1
Cause:

The image is not signed and Secure Boot is enabled.

Action:
  1. Ensure that the image is signed and that its Secure Boot settings are correct.
  2. Try to download the file in the URL again.
Solution 2
Cause:

The downloaded file is corrupt.

Action:
  1. Select a new file.
  2. Repeat the URL configuration, specifying the new file.
  3. Try to download the new file in the URL.