Please post the full formula. If you go to the formula bar you can copy the formula and paste it into your reply.
Also what are you trying to SUM()
Are you trying to SUM the results of several of your IF() statments, or is it something else.
If the part of the formula you posted is accurate, can you say why you convert 'YES' to .60 and 'NO" to N
I also note that your conversion of 'YES' is to text and not to a value. You have the .60 in double quotes, which means that it is Text. The SUM() function does not make a conversion from text to a value when the text is in a range, which may explain a result of zero.