Are you definitely in a calorie deficit? Are you tracking your intake through the day? Milk in coffee, sugar in coffee, oils you cook with, fruits… everything that passes your lips, track. Even if it’s tiny and you think it wouldn’t have an impact. It does. It’s the only way to know you’re not missing any sneaky calories that quickly add up to no longer being in a deficit.
I’ve never snacked, but I DO drink a lot of coffee and I splash milk in there. I can drink at least 10 cups a day… that’s a LOT of calories just from splashes of milk. So to maintain my weight I compensate elsewhere in my food consumption because 1) I’m REALLY short and don’t need much fuel and 2) because you don’t want to be around me without my coffee 
There are other reasons weight loss becomes difficult, PCOS in women requires a ridiculously low calorie intake to lose weight, and having an under active thyroid can also stall weight loss, until it’s managed and regulated with medication