Error 5 is the correct result if you entered the data you posted and attempted to solve for N (though not stated, I assumed that's what you were trying to do).
A principal balance of 274000 with an annual interest rate of 5% will gain about 1141.67 each month in interest, and you are specifying a monthly payout of only 800. Since the monthly interest is greater than the monthly payout, the account balance will actually increase instead of decreasing. Therefore, it will never reach a zero balance. Hence the Error 5.
Double-check your parameters to see if you're using the proper values for the problem description. Also note that since a payment is involved, you'll need to set BEG/END mode status appropriately (depends on the particulars of the problem).