It is not unusual to have a slowdown or even a slight gain in the 3rd and/or 4th weeks. During the first two weeks you dropped a lot of water and inflammation. Your body is moving past the carb cravings but isn’t very good at burning fat yet.
Stalls are weeks or months long, not days. The scale is not your most accurate tool. The first weeks of keto change your body chemistry and cause weight loss that is not necessarily body fat, after that there are other factors. Your scales will reflect hormones, electrolytes, water etc. etc. etc, not necessarily body fat.
The first week or two, the weight loss is mostly water weight. After that, your body will be healing and readjusting. Be patient, this is not an overnight weight loss process. Make sure to measure yourself as well. A stall isn’t a stall unless it’s no pounds or inches lost in at least 4 or 5 weeks.