Learn@UW/D2L - Paragraph Breaks Removed when Copying Text from Word Document into HTML Editor
If you copy text from a Microsoft Word document and paste into the HTML editor using the Ctrl+V or command+V keystrokes, any paragraph breaks and other formatting may be removed after saving.
This is a known issue.
To avoid the problem, after copying from Microsoft Word, select the "Paste from Word" icon (clipboard with the W logo on it) from the second to the last drop-down in the HTML editor to paste the text into the HTML editor window. This preserves paragraph breaks and most other formatting in the original document.