Google Spreadsheets QUERY() to combine multiple sheets, same workbook

Alternatively, you can also use query to remove the empty rows

=QUERY({'LandingPages-Oct1'!A16:F; 'LandingPages-Oct2'!A16:F}, "where Col1 <>''")

Semicolon separating sheets causes the first sheet of data to appear, but not the second

This usually means you didn't scroll to the bottom of the sheet to see the second part of data there, under all of the empty rows from the first sheet.

Since you probably don't want to import the empty rows, filter them out (by some column that is expected to be nonempty):

={filter('LandingPages-Oct1'!A16:F, len('LandingPages-Oct1'!A16:A));
  filter('LandingPages-Oct2'!A16:F, len(LandingPages-Oct2'!A16:A))}

No need for query at all; query string "select *" means you are not really querying.