What does "No Ads VAST response after one or more Wrappers" mean exactly?

When working with the VAST (and VPAID) protocols for showing video advertisements, the following error message occurs quite often:

"No Ads VAST response after one or more Wrappers"

While I have been searching the internet a lot about this, the official VAST documentation or any other resource do not seem to provide any information about the exact meaning of this error message.

Actually, most error messages are not explained like the error message itself should be self explanatory. For me they are not.

For example the Google DFP documentation: https://support.google.com/dfp_premium/answer/4442429?hl=en

Could anyone provide me with a clear explanation of this error message in specific, and maybe a resource that does explain all VAST response codes in more depth?

The response means exactly what it says.

After one or more VAST wrapper requests, with a final outcome of zero ads, the player should respond with 303 - No ads VAST response after one or more Wrappers. Also includes number of empty VAST responses from fallback.

A successful VAST response contain 0..n Ads and therefore 0..n wrappers. If each of these ads in a wrapper chain is a wrapper and ...

• each of the wrappers resources finally responded with a
  • VAST of 1..n wrapper or
  • empty VAST or
  • timeout or
  • basically everything except for an non-wrapper Ad and
• the wrapper limit (depth) wasn't reached ...

the player should respond with that error.

---

Example:
Ignoring specific VAST version implementation details

Resource 0

<VAST>
    <Ad><Wrapper><VASTAdTagURI>http://[resource_1]...</VASTAdTagURI></Wrapper></Ad>
    <Ad><Wrapper><VASTAdTagURI>http://[resource_2]...</VASTAdTagURI></Wrapper></Ad>
</VAST>

Resource 1

<VAST>
    <Ad><Wrapper><VASTAdTagURI>http://[resource_3]...</VASTAdTagURI></Wrapper></Ad>
</VAST>

Resource 2

<VAST></VAST>

Resource 3

<VAST></VAST>

---

@see VAST 3.0 - Section 2.4.1 and 2.4.2

2.4.2.1 Ad Server Details: <Error> Element
An <Error> element is also provided at the root VAST level and is primarily used to report a "No Ad" response. See section 2.4.2.4 for more information.

2.4.2.4 No Ad Response
When the ad server does not or cannot return an Ad, the VAST response should contain only the root <VAST> element with optional <Error> element.

The VAST <Error> element is optional but if included, the video player must send a request to the URI provided when the VAST response returns an empty InLine response after a chain of one or more wrapper ads. If an [ERRORCODE] macro is included, the video player should substitute with error code 303.

Besides the VAST level <Error> resource file, no other tracking resource requests are required of the video player in a nodad response in either the Inline Ad or any Wrapper ads.