Using Version 0.56.12 Chromium: 70.0.3538.77 (Official Build) (64-bit), here is how to reproduce what I am seeing.
Switch browser to fullscreen (I’m on a mac, so click the green dot, no modifier keys)
Pin one tab or more, leave them on some useful website. (May or may not be necessary, but it’s what I’ve done)
Use ⌘⇧F to hide the Toolbar.
Use ⌘T to generate a new tab
Try to go to any website (with ⌘L or other means)
You can not, unless you unhide the toolbar. This isn’t a bug per-se, it is more a user interface / usability thing. When the toolbar is hid, hitting ⌘L (Open Location) should make the URL field available to type in. If I have misunderstood how the toolbar is to be used, please point me at the documentation.