The fact that Omnis lacks support for Postgresql SSL out-of-the-box is a concern. A modern software should always use SSL. So you have to add this manually by yourself. And the Omnis documentation is not clear about exact how to do this. Some steps contains faulty or outdated information.

But thanks to Omnis Support I finally got this to work.

2. Move dll files from pgsql/bin into Program/OMNIS RT

Open the OMNOS RT folder and delete the old libpq.dll + libpq_nossl. Select and copy these files in pgsql/bin folder and copy into the Omnis Runtime application. This will enable th SSL