The basic idea is that you start a streak when you send your friend a snap, and your friend sends one back. The snaps — of course — have to be viewed to start the streak. If you do this at least once a day, you’ll see a “flame” emblem emoji next to your friends’ name after doing this for three consecutive days.
A Snapstreak or a Snapchat streak happens when you and your friend snapped each other for 3 consecutive days. The number next to the fire emoji displays the number of days you’ve been on a streak. If you’ve been on a streak with your friend for a long time, you need to keep it going.
Getting a streak back needed a lot of luck and wishful thinking at one point. However, it seems like Snapchat has eased up quite a bit in terms of restoring Snapstreaks. It’s best to contact Snapchat as soon as you noticed that you lost your Snapstreak.
If you know that you have consistently sent a snap to your friend and vice versa, you can get that streak back by contacting Snapchat support directly.