404 Error when specifying a port

Question

I have a legacy app written in VB6 and uses the IEFrame.dll that recently broke due to a server change. I'm trying to debug why it broke, but I can't get it to work on my local machine. On my local machine the URL is like:

http://localhost:4200/landing

If I navigate to http://localhost:4200 the page loads, but if I try and navigate to http://localhost:4200/landing I get a 404. If I try that same URL in FF or Chrome it works as expected.

So is there a way to get the WebBrowser control from IEFrame.dll to work when the port is in the middle of the URL?

This is basically what the VB code looks like:

Dim url As String
url = "http://localhost:4200/landing"
wb.Navigate2 url 'This works if there is no port specified

"Landing" is an Angular route. I'm new to Angular and didn't actually write this particular server code so I can't say for sure if there is a redirect or not.