Hello,
Typically 443 is the default port - however it could be different. For example, in the screenshot I put in, our port for ERP is not 443 - so the port must be left out - the reverse proxy fills it in.
However, this is probably not the case for you. A 404 means the service cannot be found - if you sure they are same (I don't think they are - look for an extra space, : - something) - just undeploye the iflow in HCI and re-deploy - you can also redo the communication arrangement. There could be something very small missing - why don't you take the both and copy/paste to notepad and compare. I do that sometimes to find a small error.
-ginger