Under Nest

Are you have problem with your MyBB? like this picture

SQL Error:
2002 - Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

Query:

[READ] Unable to connect to MySQL server

You must check your MySQL Service, if you're the root / provider service of web hosting, you must check your MySQL, this problem is caused your MySQL are Offline. you must check or restart the MySQL. 

you can use this code in your MySQL 

chown -R mysql /var/lib/mysql/* chgrp daemon /var/lib/mysql/*

If you are client, you must contact the host provider for fix it.

moreover please backup your file in hosting. 

if you have problem for backup, you can check > Here <