I think there are two different problems:
looks like your CODE can’t accesst your cloud - look at DNS, routing etc (see Collabora integration guide for details)
sounds like CODE doesn’t trust the instance accessing the endpoint. same advice… likely
- Important changes regarding COOL/CODE docker versions from v21.11.3.6 on (multiple domains setup)
- likely wopi_allowlist Search results for 'Requesting address is denied' - Nextcloud community and Search results for 'Requesting address is denied' - Collabora Online
help to fix the problem