Are you copying and pasting the data from Excel, or using Mail Merge.
If copying and pasting, select the row above the Total row and then use Paste.
Note, the settings under File>Options>Advanced>Cut, copy, and paste may have been changed. Or, under File>Options>Advanced>Editing options>Typing replaces selected text.
Copying and pasting data from excel. Your second note of changing "Typing replaces selected text" made the table paste correctly, but at the bottom of the table I use a sum above function and that doesn't seem to be working.
This is happening on multiple computers where previously there was no issue at all. I wasn't sure if there was some kind of update that broke the functionality.