Prototype Testing On Device - Incorrect Screen Size

I have a prototype for iPhone 6/7/8 with all artboards at 375x667, scrolling set to none, and nothing scrollable in length/height in the prototype.

When I run a desktop preview...it works fine.

When I test it on my plugged in device (iPhone 6)...it works fine.

When I add the published link to my home screen so it looks like an app on my phone, and I press it to load the link...it works fine.

HOWEVER, When I test the published web link, on a device like normal, without adding it to the home screen, the prototype appears larger than the screen so the viewer must scroll up/down to see the entire prototype. It appears as though the top, left, and right sides are all aligned correctly, but the bottom is being stretched to make the prototype longer/taller.  Or, is this something like the web browser not scaling correctly, some user error like I might have changed a setting somehow, etc?

Can anyone tell me why the normal published link would not display correctly?

Thanks!

Attached Images:

1. Loading as app on homescreen, or previewing on desktop, or previewing on plugged in device

2. How the actual published link loads when I send the link to someone and they click on it.

3. Needing to scroll up after loading the link.