Can't connect to local server in any internet app? I have a local server set up on my network at 192.168.1.9

All of the other computers on my network can connect to it fine.

It's definitely on the same wifi network, and I've tried disabling mobile data to make sure it's only using the wifi.

When I try to connect to it on my phone, it just says 'This sit can't be reached.  ERR_ADDRESS_UNREACHABLE

I've tried Firefox and Chrome, and nothing is working. Is there some setting I don't know about that is preventing my android from connecting to stuff on the local network? I've also had trouble playing multiplayer mobile games in the past, which may or may not be related.

It's a Google Pixel 2.
Some Wi-Fi routers have by default an option enabled that prevents communication between each other Wi-Fi devices (or sometimes even prevents communication to all LAN devices). 

You should check your router if there is such an security option and disable it if it exists.