Issue running mmomni reconfigure

I set up a self-hosted mattermost platform for my research team. I used Mattermost Omni with mattermost server version 9.1.0 installed on a remote Ubuntu v20.04 Desktop server on which I don’t have the root rights. During the installation I had to use MMO_HTTPS=false. The Network Admin of my server set up a custom nginx reverse proxy. The mattermost domain has been hosted and runs properly with an HTTPS connection.

I wanted to enable plugin uploads. I followed the documentation on the Omni webpage but when I run the command “sudo mmomni reconfigure” I am getting the following error

I am not a systems or network engineer so could you please help me understand what has or where have I gone wrong. I did the steps of mentioning the nginx_template in mmomni.yml file as well.

Kind regards,