To me it sounds like a "pat" answer from the storekeeper. However, if it boots, then turns off, I would say the simplest thing would be a stuck switch. Worst case, you need a new MB. It depends on how it shuts down. If it doesn't ask for confirmation to shut down, I think it would be a MB problem.
1 
not enough info to analyze
bill さんによる
My phone is not opening whe I go to the shop the shopkeeper said the ic not working
up_52 Gamers さんによる
To me it sounds like a "pat" answer from the storekeeper. However, if it boots, then turns off, I would say the simplest thing would be a stuck switch. Worst case, you need a new MB. It depends on how it shuts down. If it doesn't ask for confirmation to shut down, I think it would be a MB problem.
bill さんによる