Hi @McJagger – big fan of your music! Let’s see if I can help…
Before I get started, I wanted to suggest using metafield definitions via the GraphQL API. You can apply a metafield definition to all of your orders (under a given namespace and key) which can help validate your metafield data moving forward!
To create a metafield on an order using the REST API, you’ll need to POST your data to:
https://
> *I can manipulate an existing field, but not create an entirely new one.*
That suggests to me that you might be using the wrong [HTTP method](https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods) to update your metafields. According to the [REST API for metafields](https://shopify.dev/api/admin-rest/2022-01/resources/metafield#top):
- POST – Creates a new metafield for a resource
- PUT – Updates a metafield
Always be sure to use the right **method and URI**.
Finally, I also wanted to mention that [response code 1 is not a standard response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status). Sometimes you can get a response code of -1 when you're having network or connection issues, so there might be an issue with your network. Hope that's helpful!