Eraser tool does not "mend" surfaces

Hi all.
I just upgraded from a 2017 version to the latest version. I have been using the eraser tool to remove lines on a surface and when I do the surface remains broken into several pices. My understanding was that the surface should go back to one unbroken unit. What am I missing here?
Thanks.

Sounds like you are hiding the edges rather than deleting them.
Shift with eraser will hide, ctrl with eraser will soften. Both work as a toggle and show an extra bit to the cursor when active.

Option on Mac.

Is it in fact “a surface” and not several that may not be quite coplanar?

Thanks for all the prompt replies. I was holding the shift key, as I saw it in a Sketch Up video on their website. Problem solved.