This usually occurs when the KPI is assigned a unit of measure that has a display factor of 0, hence the calculation becomes value*displayfactor = value*0 = 0.

 e.g. a Percentage unit of measure will have 100 as a display factor, so a value of 0.4568 becomes 45.86%. 

To correct this issue navigate as follows (You will need to have permission to edit the measurement types):

Administration -> Units of Measure. (Leave the Display Factor blank or set it to a non-zero number)

Values will also not be displayed if they are not within the specified Min and Max values on the filters.