Hello @grumo
I’m not sure that I understand your whole installation steps, but I assume that the best way to deploy Document server on the server without access to Internet is the docker installation. Could you please follow and check the result?
Download image with ONLYOFFICE Document Server from the official repository from the DockerHub on a server with Internet access using command: sudo docker pull onlyoffice/documentserver
Save image as files with the command: sudo docker save -o documentserver.docker onlyoffice/documentserver
You can post your whole guide here, so it will help other users in the same situations. The guide which I posted was tested before (docker), so it should work. But if you want to share your steps, please feel free to do it.