Hi @YutaNagaoka,
Here are some additional questions to help troubleshoot this:
- What happens if you try Ctrl+R or Command+R?
- What Mattermost server version are you on?
- What is the device (webapp, desktop app) and what is the browser (Windows, Mac, etc.)?
- Can you also help send/check the contents of the Developer Tools Console?
- To increase log level, you can do the following: Set the File Log Level to Debug: Go to System Console > General > Logging and set File Log Level to DEBUG. If you can’t access the System Console find this line in config.json
This thread might also help: [SOLVED] Server started but app not connecting and no logs