Map server is not available?

I was following this tutorial on setting up the game server on Digital Ocean. https://suriyun-production.github.io/mmorpg-kit-docs/#/dedicates/digitalocean

I was able to link to the server and log into the character selection window. However, when I tried to start the game, I got an error message saying the map server is not available. I exported the server from Unity and uploaded it to DO using Cyberduck. If you have done this before, please let me know where can I begin to debug this error? Would this be a server(unity) issue? or there is something I missed on the DO side? Thanks so much for your time.

Screencapture of the error: Example link

best,