My young corgi puppy suddenly refuses to play fetch after a scary thunderstorm

I recently got a 4-month-old corgi puppy who was absolutely obsessed with playing fetch. We’d spend at least 30 minutes a day in the backyard tossing his favorite ball, and he’d come bounding back every single time, tail wagging like crazy. But a couple of nights ago, we had a pretty intense thunderstorm with loud booms and flashing lightning. Since then, every time I try to grab his ball or even say "fetch," he hides behind the couch or just looks at me like he doesn’t understand. I’ve tried lots of gentle encouragement, sitting quietly with him while holding the ball, and even playing soft music to calm him down, but nothing seems to bring back his usual excitement. I really want to help him get over whatever’s frightening him so we can enjoy our playtime again. Has anyone else’s puppy had a similar setback after a storm? How long did it take for them to bounce back? Are there specific things I can do to gently rebuild his confidence around playing fetch?