Without seeing your specific situation, I cannot say whether this is what's causing your issues or not, but this is my best guess.
WordPress has this cool thing called the Heartbeat API. It pings the server periodically while you're logged in and in the WordPress admin. It does a number of things to help improve the editing experience like auto-save, check if you're logged in, check if someone else is editing your page (or kicks you off), etc.
If the heartbeat doesn't execute successfully (or a variety of other situations), it can cause things like the publish button to be disabled. This is actually a good thing since it prevents you from trying to publish without a connection to the server (and potentially losing your work).