The code returns the following error:

Registration error: Failed to save to Google Sheets

  at Module.POST (/app/api/register/route)
  at async handleSubmit (/app/register/page)

Revise the code to address the error.

I was previewing: /register

The code returns the following error:

Missing required environment variables

  at Module.POST (/app/api/register/route)
  at async handleSubmit (/app/register/page)

Revise the code to address the error.

I was previewing: /register