This may bear some resemblance to your table.
one of the columns has drop downs.
(in Numbers, these are "popup menu cells")
These use If formulas to populate a number in another column.
(actually, the formulas uses the values in these cells to determine a value and enter it
into the cell containing the formula.)
I want to add that entire column, but it's not adding, nothing is happening.
It's like it's not recognizing it as having any values at all. What am I missing?
(Insufficient information.
What have you done to tell Numbers to sum that column?
If your answer is 'nothing'. that would explain the lack of action from Numbers.
If your answer is anything other than 'nothing', then sharing your description of what
you have done would likely provide a hint to the answer to "What am I missing?"
While waiting for your information, you might take a look at this example.
The formula does not use IF, but other than that, it does what I think you are trying to do.

Values in column C are determined by user choice from a popup menu in each of the cells, containing a list of the values "none" (which displays as a blank cell) and "Item 1" through "Item 9".
The formula shown below the table is entered in cell E2, then filled down to cell E10. Inthe formula, RIGHT(cell) gets the value (a text string) from the referenced cell and returns the last character in that text (a digit from 1 to 9) to VALUE. The VALUE function accepts that text value and converts it to a number, which is then multiplied by 100. The result is placed in the cell containing that copy of the formula.
Row 11 has been converted to a Footer Row.
The formula in E11 is SUM(E)
The formula returns the sum of the numbers in all non-header and non-footer cells in column E of the table.
A screen shot of your table and copies of the formula(s) you are using would help refine the notes above.
Regards,
Barry