Perhaps a fixed row height has been specified, in which case excessive text
won't be visible. Right-click the table and choose Table Properties from the
context menu; look at the Row tab of the dialog box. Clear the "Specify
height" option if it is selected. Note that you can use the Previous Row and
Next Row buttons to move between the table rows.
And another possiblity... is that the cell has an indent too large for the
cell and the text is outside the cell borders. I have seen this many times,
especially when the table has been pasted from another document with clashing
styles.