"Failed to verify username!" error occurs when minecraft has problems connecting to login server.

Steps to fix this.

1. Open your server hosting control panel at https://lemehost.com/server/index
2. Select your server
3. Stop server
4. Click "File Manager"
5. Edit "server.properties" file
6. Locate "online-mode=false" and replace it with "online-mode=true"
7. Save file
8. Start server