The PMT functions may not work due to the following reasons: 1. We provided the rate argument as a negative value or the nper argument value as 0 to the PMT(). 2. We entered the PMT() argument as text values. 3. We did not supply the rate argument as a percentage value or the argument pv (loan amount) as a currency value to the PMT(). 4. We did not apply the PMT() according to the specific loan payment frequency.