unable to establish remote connection to mariadb (mysql) on centos7 on gcloud from mac or gscipt

newbie here
- Issue: unable to establish remote
connection to mariadb (mysql) on centos7 from a mac or a gscript
- setup: I
got 2 lamp machines: one test (107) and another one production (35)
107 -
centos6.5 with mysql (vps in digitial ocean)
35 - centos7 with
mariadb-server-5.5.52-1.el7.x86_64 (compute engine on
gcloud)

db,dbuser,dbpass and port (3306) same on both
machines

• problem
  details:
  I can establish a remote and a jdbc connection to mysql on 107 (test
  server) from a mac using nc, mysqlworkbench and a gscript app; but when I try to get a
  connection going with 35 (prod server) with the same user/pass/db parameters I get this
  response:
  workbench: Can't connect to MySQL server on '35.190.134.164'
  (60)
  gscript (jdbc connection exception thrown): Failed to establish a
  database connection. Check connection string, username and password.
  nc on
  mac: ... (literally nothing after issuing the command nc <35's ip address>
  3306

-What I
tried:
1. href="https://mariadb.com/kb/en/library/configuring-mariadb-for-remote-client-access/"
rel="nofollow
noreferrer">https://mariadb.com/kb/en/library/configuring-mariadb-for-remote-client-access/

my.cnf in 35 looks like
this:

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock

#
            Disabling symbolic-links is recommended to prevent assorted security
            risks
symbolic-links=0

# Settings user and group are
            ignored when systemd is used.
# If you need to run mysqld under a different
            user or group,
# customize your systemd unit file for mariadb according to
            the
# instructions in
            http://fedoraproject.org/wiki/Systemd



#skip-networking
bind-address
            =
            0.0.0.0


[mysqld_safe]
log-error=/var/log/mariadb/mariadb.log
pid-file=/var/run/mariadb/mariadb.pid

#
#
            include all files from the config directory
#
!includedir
            /etc/my.cnf.d

start="2">

firewall-cmd looks like this (for active and
public):

trusted
(active)
target: ACCEPT
icmp-block-inversion:
no
interfaces: eth0
sources:
services: http
https

ports: 3306/tcp
protocols:
masquerade:
no
forward-ports:
sourceports:
icmp-blocks:

rich rules:
public
target:
default
icmp-block-inversion: no

interfaces:

sources:
services: dhcpv6-client http https ssh
ports:
3306/tcp
protocols:
masquerade: no
forward-ports:

sourceports:
icmp-blocks:
rich
rules:

start="3">

the dbuser its password is not the issue as I created
the same user and password for the same database on both 107 and 35. the user has only
usage privileges (select, update, delete, insert) and is set as % on both
machines.

I've been on
this for 3 days now and I'm not close to figure this out. any help is appreciated. what
am I missing?

Thank you.