DIAGNOSIS You've likely tripped the electronic overload protection. It's not a mechanical failure; the saw's brain is just taking a nap because it got too hot or bogged down.
FIX First, pull the trigger and hold it for a solid 3-5 seconds. Sometimes that resets it. If that doesn't work, pull the battery off, wait 30 seconds, and pop it back on. Try the saw. Still nothing? Try a different 20V DeWalt battery you know is good. The problem is almost always the protection circuit or a battery communication hiccup.
IF THAT DIDN'T WORK If a known-good battery doesn't fix it, the issue might be the trigger switch itself. It's a common wear point. You'd need to open the handle housing to check for a broken wire or a failed switch, which is a job for DeWalt service or a confident DIYer with the right tools.
HEADS UP When you get it running again, avoid forcing the saw through thick material or using a dull blade. That's what causes the overload to kick in. Let the tool do the work at its own pace.