Magento 2 Error – User Already Has More Than ‘max_user_connections’

General error: 2006 MySQL server has gone away is a very generic error. It can be fired due to very different reasons. Usually, it happens with slow (until timeout) or very expensive queries

Looking your code trace, it seems it is just Magento default code (no extensions involved), so I bet your database is bigger than your MySQL resources can handle, or maybe your MySQL configuration is not correctly tuned to run a Magento application

In both cases, your hosting provider should give you an answer or recommendation

After copy the files, you check to changes database connection at

/var/www/html/sitespi/app/etc/env.php

 'db' => 
  array (
    'table_prefix' => '',
    'connection' => 
    array (
      'default' => 
      array (
        'host' => '[Yourhost]',
        'dbname' => '[DBName]',
        'username' => '[DbUser]',
        'password' => '[DbPassword]',
        'active' => '1',
      ),
    ),
  ),

Then put the proper mysql access at there

After that You should Delete all clear cache by deleting files from

• /var/www/html/sitespi/var/cache
• /var/www/html/sitespi/var/page_cache

Also if you have any cache like redis ,memcache then flush it.

Most import, you need to check your database user has enough User privilege for that database.