The reasons are as follows: First, the connection to the server failed, and the most common problem is the local network problem. First, open the browser and check whether there is a problem with the network. If you can't access the Internet, you are advised to check the network problems yourself. 2. Reason 2: The server is under maintenance. Check whether the server is under maintenance, or try again in the morning and when other users are few. 3. Reason 3: Cache problem, you can use anti-virus tools to clean the cache. 4. Reason 4: There is something wrong with the software version and it should be updated.