You have a typo in your -e PORT:8996. This must be = instead of ::

-e PORT=8996

But this configuration setting is non-useful and add complexity. Best is to remove -e PORT=8996, openproject will still listen on 80 within the container, but your -p 8996:80 will make openproject listen on another port on your host.

For your "Invalid host_name configuration" error, did you well access openproject using http://localhost:8996? (we cannot see the whole URL you posted, it seems truncated)