Hey @eapariciodev
Thanks for reaching out for help with this! Can you share what you are using to code the custom header?
@stephen.trumble I'm not sure what you mean. There is no code. It's just a Flow with a Webhook block in it. The webhook body is just the default that has the profile email. We then add a header, which is just a static header name and value.
When the flow triggers then webhook is sent, but it does not contain the header we configured.
Hi @eapariciodev!
May I ask how you are able to determine that the webhook is sent but the header is not configured? Also, may I ask what is the nature of the URL you are calling (Is it a third-party tool like Zapier, or a custom server/tool that is proprietary to your site/business)?
Finally, can you confirm that Multi-Factor Authentication is enabled in your profile, as this is a pre-requisite for enabling webhooks?
These questions will help myself and other Community members to understand the issue better so that we can get to the bottom of it faster.
Thanks for using the Community!
- Brian
@Brian Turcotte The webhook points to a custom server. We know it is being sent because Klaviyo shows it as sent and we receive the request. However, the request does not contain the custom header.
To reiterate, this is only happening on new flows we set up a few days ago. We have identical flows for other clients which are working fine.
I've also set up a test on my own account with the same result. For that one I'm using the Pipedream service which let's me see the raw request data coming in.
Yes, I do have MFA enabled. I can make the webhook live and they are triggered, they just don't include the custom header.
This is frustrating, but I’m at least seeing some progress. I’ve made no changes to my test flow. I just keep triggering it a few times a day just hoping Klaviyo has fixed it.
The latest result:
At least now the webhook request included the custom header. The problem is that the value is not correct. It is the semi-masked value that is displayed in the flow editor.
I set the custom header value to something like “abcde_123456789”. The value I received is “abcde_1########”. 
Hi @eapariciodev!
It turns out that several similar cases occurred during the same time period as you reported this issue, and Support was able to identify a bug that has since been fixed. If the webhook still isn’t working, you may be able to resolve the issue by simply starting over with a new flow with the same structure.
If that doesn’t resolve the issue, feel free to reply and we can take it from there.
Best,
Brian
