Can't open a specific website running on localhost on my iphone

I have two websites, both made in vue, running on vue dev server on my mac. One is running on localhost:8080 and one on localhost:8081. My ip address is 192.168.0.168. On my iPhone, I can open the website on localhost:8080 but not the one on localhost:8081.

I have tried to switch ports so I put the website that I can't open (the one that was on 8081) on 8080 instead, but I still can't open it, and I can still open the other website when it is on 8081 instead.

Basically, I can open one but not the other. Both work perfectly on my mac btw, accessing them on localhost:8080 and localhost:8081 on my browser (chrome or safari).

When I try to open the buggy website, I instantly get the message

Safari cannot open the page because it could not connect to the server.

What could be the issue here? Could the website be too large (too much data)?