Thank you for the suggestion. I've removed all special characters, and it's still encountering an error. { "_engineData": { "calledAt": ...

To further troubleshoot this issue, I installed the Integromat DevTool extension for Chrome. I then inspected the request body for callin.io's Create ...

Good point! I neglected to mention that I've experimented with both including and excluding braces { } in the body. I've also attempted prepending -F ...