I am hosting a shiny server on Ubuntu 16.04, and am using Ngnix for authentication. The server worked fine until recently it only stopped allowing multiple user use it at the same time. When a new user logs in, both the new user and the user currently using it will be kicked out, and whoever refresh the web page first will get in, and both users will be kicked out again once another person tries to get in. The screen will just grey out and "Disconnected from server" will show up in the bottom left corner.
There is no error in the log, the following will show up in the browser console. I haven't made any changes to the code in a long time, the only changes I made recently was updating R from 3.3 to 3.4 and R studio to the latest version last week. I also installed the latest version of shiny server after encountering this problem.
Any help will be much appreciated!