Not sure if this is the issue -
On the boss's PC, from the Ribbon select 'Review'
In the Tracking section look at the options in the top-right drop-down.
If it is just 'Final' or 'Original' - he/she will not see the changes (markup).
Select 'Final showing markup'
If this doesn't work look at the next drop-down 'Show Markup' and make sure that Insertions and Deletions is checked.