Can no longer connect to localhost on mobile via computer's IP Address + port

For months I have been connecting to my localhost on my [device] via computers.ip.address.x:port (both devices on exact same network), but I've noticed that each time I've tried over the last month, I can't ever get to the localhost. It's like I've accidentally messed with something on my macbook that is preventing this, as it doesn't work on any network.

This is now a huge issue as I can't do any mobile testing. Any help, ideas, etc., are much appreciated and I'll be on standby all day to fix this!

Thank you!

Oh, I do remember something that happened around the time it stopped working (I think it was around the time), is I began using a VPN, but I've been trying to connect to my localhost only OFF or DISCONNECTED to my VPN service, so I'm not sure if there is an issue with having used a VPN daily that's making this wonky.