Your site is down. First, check the database name, user, password, and host in...

https://uniform-wiki.win/index.php/Should_I_Restart_MySQL_When_WordPress_Cannot_Connect%3F

Your site is down. First, check the database name, user, password, and host in wp-config.php, then see if the server is up. Next, check access rights and repair the database. If you cannot reach the server or verify its details, call your host for help.