Codered form page submit gives 500 error

[bradrice]

I'm trying to use a coderedcms form page to create a contact form. It works fine, echoing to the command line locally, but when I use it on my server I get a 500 error when I submit. I don't get anything very useful in the logs to figure out what is going on. This is my prod setup for the anymail setup to send email to the Mailgun api. I also can send using the command line with curl from the server.

EMAIL_BACKEND = "anymail.backends.mailgun.EmailBackend"
DEFAULT_FROM_EMAIL = "[email protected]"
SERVER_EMAIL = "[email protected]"
MANAGERS = ADMINS
ANYMAIL = {
    "MAILGUN_API_KEY": os.environ.get("MAILGUN_API_KEY"),
    "MAILGUN_SENDER_DOMAIN": "mail.oh-joy.org",
}

I don't see anything in the docs to help me. I do find the submission is putting the form into the sqllite3 db fine, but when it submits I get

Internal server error
Sorry, there seems to be an error. Please try again soon.

Any help would be appreciated.