it may be brick-changing. brick-changing of mobile phone is mainly caused by cracking the system authority through ROOT mobile phone, or brushing into unofficial system and cracking the system standard of mobile phone (for example, the mobile phone is cracked into Unicom mobile phone). if the mobile phone is brick-changing, it can't be operated and used. Please take the purchase invoice and warranty card with you and send them to OPPO customer service center for processing.