Unable to Connect to Form Server

1. What is the problem? Be very detailed.

When logging into my domain that has custom SSL, I am able to upload forms, use Collect to submit forms, however on the submission page the form server is unable to start and is returning a 400/403 error.

2. What app or server are you using and on what device and operating system? Include version numbers.

Running ODK Central v1.1.2 via Docker

3. What you have you tried to fix the problem?

Re-building ODK Central but the issue continue to persist.

4. What steps can we take to reproduce the problem?

5. Anything else we should know or have? If you have a test form or screenshots or logs, attach below.

What operating system are you using? Have you tried the steps at https://docs.getodk.org/central-troubleshooting/#preview-could-not-connect-with-server?