How do I fix VAST-2.0-linear-mediafiles?

Add ` ` containing at least one ` ` element with a valid video URL inside ` `.

What does the VAST error " must contain with at least one " mean?

A ` ` creative with no ` ` — or with an empty ` ` container — has nothing to play. At least one ` ` element is required.

VAST-2.0-linear-mediafiles

<Linear> must contain <MediaFiles> with at least one <MediaFile>

ErrorRequired fieldsIAB VAST 2.0 §2.4.1VAST 2.0 and later (all versions)

A `<Linear>` creative with no `<MediaFiles>` — or with an empty `<MediaFiles>` container — has nothing to play. At least one `<MediaFile>` element is required.

How to fix

Add <MediaFiles> containing at least one <MediaFile> element with a valid video URL inside <Linear>.

Invalid

<Linear>
  <Duration>00:00:30</Duration>
  <MediaFiles>
  </MediaFiles>
</Linear>

Valid

<Linear>
  <Duration>00:00:30</Duration>
  <MediaFiles>
    <MediaFile delivery="progressive" type="video/mp4" width="1280" height="720">
      <![CDATA[https://cdn.example.com/ad.mp4]]>
    </MediaFile>
  </MediaFiles>
</Linear>

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Other Required fields rules

VAST-2.0-root-elementRoot element must be <VAST>VAST-2.0-root-version<VAST> must have a version attribute VAST-2.0-root-version-valueVAST version attribute must be a recognised version string VAST-2.0-root-has-ad-or-error<VAST> must contain at least one <Ad> or <Error>VAST-4.0-wrapper-root-error<VAST> root contains both <Ad> and <Error> elements (invalid per VAST 4.0)VAST-2.0-ad-has-inline-or-wrapperEach <Ad> must contain exactly one <InLine> or <Wrapper>VAST-2.0-inline-adsystem<InLine> must contain <AdSystem>VAST-2.0-inline-adtitle<InLine> must contain <AdTitle>