Howdy, Belter. When you roll a failure on the Payday move, the payday is junked and unsalvageable...unless you spend a Grit. Like any other roll, you can spend a Grit to take the 4/5 result. Means you can choose 2 of the bullet-pointed bits of good news to be true. From there, handle it as normal.
If you don't spend a Grit when you fail a payday roll, you don't have to pick any negatives--because you're looking at a big useless chunk of slag where you were hoping a payday was.
Hope that's clear as mud for y'all. Let me know if y'all got follow-up questions.
Chariot, out.