Chrome error causing embedded Marketo form to not display | Community
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Sheila-ontic
Level 1
March 23, 2026
Question

Chrome error causing embedded Marketo form to not display

  • March 23, 2026
  • 1 reply
  • 13 views

We have had a Chrome problem for a while and are trying to get to the bottom of it. Most people do not have issues, but for some employees (and not all the time) there is an issue with embedded Marketo forms not displaying. We are concerned this is happening with others as well so are trying to dig in further. It is only Chrome that has the problem. The page is: https://ontic.co/demo-request/ although other pages with Marketo forms also have the same issue (when someone is having this problem). Here’s the console errors when this is happening. 


From a Gemini search, one of the suggestions is that we need to:
update the Access-Control-Allow-Private-Network: true header added to the preflight (OPTIONS) response for our instance in the CNAME. Because go.ontic.co is managed by Marketo's infrastructure, you often have to reach out to their technical support. They recently updated their infrastructure to handle this for many customers, but older instances or specific CNAME setups sometimes get missed.

This instance is from 2021 so it is older, but not that old. Does this make sense? I haven’t been able to figure out how to see if the Access-Control-Allow-Private-Network is set to true.

If this is correct, happy to ask Marketo Support to fix. Just want to see if there are any other ideas on what is happening.

 

    1 reply

    SanfordWhiteman
    SanfordWhiteman
    Level 10
    March 24, 2026

    The PNA header error is at best a symptom of an internal misconfiguration (i.e. at Ontic). You never need that header when loading Marketo forms on public websites (e.g. accessing https://go.ontic.co from https://ontic.co or from https://anythingelse.example.com.

     

    You mention “employees” seeing this error, which sounds like a clue. Are they on your private network (incl. VPN) when they see it? Because one misconfig that would cause this is when your IT team routes some “local-looking” resources to local IPs. If, when you access https://go.ontic.co internally, you‘re routed to an IP like 10.0.0.10, Chrome considers that a private network and subject to additional CORS restrictions. It’s considered a private network even if 10.0.0.10 is a reverse proxy that connects under the hood to Marketo — the browser just sees it as 10.0.0.10, which is private.

     

    The solution is to make sure even internal users hit the public IP of Marketo’s webservers (104.17.73.206, etc.).

     

    The good news is if this is the cause, it cannot be affecting anyone outside your private network!

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