Magento 2 – Fix MySQL Server Has Gone Away Error

I managed to migrate magento 1 to new magento 2.2.5
When I reindex for the first time I get in indexer

Category Products

[2019-02-07 21:58:57] main.CRITICAL: Warning: PDOStatement::execute(): MySQL server has gone away in /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Statement/Pdo.php on line 228 {"exception":"[object] (Exception(code: 0): Warning: PDOStatement::execute(): MySQL server has gone away in /var/www/html/vendor/magento/zendframework1/library/Zend/Db/Statement/Pdo.php on line 228 at /var/www/html/vendor/magento/framework/App/ErrorHandler.php:61)"} []

mysql.conf settings are:

[mysqld]
#
# * Basic Settings
#
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /var/lib/mysql
tmpdir          = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address            = localhost
#
# * Fine Tuning
#
key_buffer_size         = 512M
max_allowed_packet      = 1024M
thread_stack            = 192K
thread_cache_size       = 256
connect_timeout=320 # default 10
table_open_cache = 4096
table_definition_cache  = 4096
sort_buffer_size        = 16M
max_heap_table_size     = 512M
tmp_table_size          = 512M
interactive_timeout     = 3600
max_connections         = 400
max_connect_errors      = 1000000
skip_name_resolve
#skip_secure_auth
wait_timeout            = 28800
innodb_buffer_pool_size = 2G
myisam_sort_buffer_size = 128M
innodb_log_file_size    = 256M
innodb_thread_concurrency  = 18
innodb_flush_log_at_trx_commit       = 2
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover-options  = BACKUP
#max_connections        = 100
#table_open_cache       = 64
#thread_concurrency     = 10
#
# * Query Cache Configuration
#
query_cache_limit       = 1M
query_cache_size        = 64M
query_cache_type        = 1

Tried to increase the limits in mysql with no luck.
Any suggestions please?