1, unstable network connection or network failure.
2. System maintenance or upgrading causes the system to be temporarily unavailable.
3, the user fills in the information is incomplete or fill in the error.
4, if you encounter a situation that can not be submitted, you can try to reconnect to the network or wait for the system to return to normal, and at the same time to check whether the information filled out is correct.
5, if the problem still exists, you can contact the system administrator or the relevant technical staff to resolve.