What's here, where it isn't working? What version of Word?

To have a landscape page in the middle of portrait pages, it must be
preceded and followed by a Section Break (Next Page).  So when you put in a
section break, you may have added an extra section without text that you
probably need to get rid of.

Click ¶ on the formatting toolbar to show nonprinting characters, including
section breaks, so that you can see what is really going on.

Assuming all your landscape sections are 1 page, this is a clever way to
hide the headers on them. But this:

Doesn't sound like the right way to do it.  Go to File | Page Setup, Layout
tab, and make sure "different first page" is checked under Headers and
Footers.

Then, when you go back into Print Layout, and view Headers/Footers, you
should see that the header/footer for each landscape section is labeled
First Page Header.  Delete whatever is in there.

Hope that helps,