1. QR code has expired: QR code has only a certain validity period. If the scan has expired, you will be prompted with a code error. You can try to get the QR code again and scan it within the validity period.
2. Mobile phone network problem: the mobile phone network is unstable or the network connection is slow, so it is impossible to scan the QR code. You can try to switch the network environment, or try again after the network connection is more stable.
3. The WeChat version is too low: If the WeChat version is too low, it will lead to code errors when scanning the QR code. You can try to update the WeChat version and try again.