I feel very dumb for asking, but this Nashville Hot Chicken recipe isn't spicy enough, and I don't know why nor how to tweak it...

The writer is a burger station cook at an international school in Asia and creates a weekly special burger. They attempted to make a Nashville Hot Chicken sandwich using Sam the Cooking Guy's recipe. The recipe includes cayenne, brown sugar, garlic powder, paprika, chili powder, and red pepper flakes, with a spiced oil sauce for dunking the chicken. The writer scaled up the recipe to accommodate the lunch rush. However, they found the resulting sandwich to be sweet but not spicy enough. They tried tweaking the recipe by increasing the spicy components and reducing the brown sugar, but it didn't make a significant difference. The writer is struggling to understand why the increased spice didn't make the sandwich hotter. Despite this, their boss wants to feature the sandwich as the weekly special next week. The writer is seeking recipe tweaks or alternative recipe recommendations to improve the sandwich. They are looking for help to make the sandwich spicier without making it one-note.