“ChatGPT Plus” and “OpenAI GPT-4 API” models are two separate products.
You might have bought the consumer chat “Plus” version at chat.openai.com, which is NOT compatible with Make.
OpenAI APIs for developer / “commercial” use does not have any free plan.
You can buy credits on the OpenAI Developer Dashboard, under Accounts > Billing page
Next, go to the Usage Limits page, and set the Monthly budget field to the same as the value above (e.g.: 120), then save your changes.
