Please remember yes a calorie deficit is key for fat loss BUT the below also play a role in your scale weight:
Having more salt and the types of seasonings in food the previous day.
Later dinner so it's not digested.
Inflammation from walking a lot or doing a workout in the previous days
Stress, yep, even stressing about the next days weigh in and or hormonal?
Drinking more water than usual or upped intake.
You may have digested food in your system still because haven't used to toilet yet.
Have you honestly tracked everything including dressings, milk in drinks, sauces and seasonings etc?
Remember too that fitness trackers and fitness machines are not accurate with calories out either so best not to rely on them and try not to 'eat back' as you may think you've burnt 500kcal and eat back 300kcal but actually you only burnt 300kcal and you're then eating 300kcal.
If you've drunk your water, hit your steps, done your workouts and eaten more nutrient dense foods than less nutrient dense foods all week that's a bigger win than what scales say. Don't let it dishearten you and get you down or go too hard on the exercise and cutting food the following week to 'make up for it' just carry on, consistency creates habits which make it long term sustainable.
If you stagnate or gain for a few weeks consecutively, consider tweaks but don't let the scales get to you. It's hard not to get frustrated but remember it's a lifestyle change and bodies are complex things