Golang/Terraform Custom Provider - HCL Output Error

Hi there, I am building a custom terraform provider and it is working for the most part, with exception that when I try to create a resource, it shows me the plan, but errors out with an unformatted JSON output instead of the Terraform HCL. The interesting bit is that it does successfully create the resource in the administrator portal, but terraform is not building the state file, which would allow me to also destroy that resource later. I have a couple of data sources which works fine without any problems, and the state file is created successfully.

Seems to me that the conversion from JSON to HCL is not happening, but I can’t spot why.
Below is a snippet of my api client. Any assistance is appreciated. Thank you