Port number in URL

Can I include a port number in a plugin URL?
I need to call an URL looking like:

But I get:
There was an issue setting up your call.
Sorry, we ran into a temporary bug and can’t complete your request. We’ll fix it as soon as we can; please try again in a bit!

There doesn’t seem to be any attempt to make the API call.

But, if I remove the port number an API call is attempted. So, it looks to me like the Bubble plugin builder does not support port numbers in the URL.

Many thanks, Rob