Did you set the bind option to allow remote access on the redis server?
Before (file /etc/redis/redis.conf)
bind 127.0.0.1
After
bind 0.0.0.0
and run sudo service redis-server restart to restart the server. If that’s not the problem, you might want to check any firewalls that might block the access.
Important: If you don’t use a firewall (iptables, ufw..) to control who connects to the port in use, ANYONE can connect to this Redis instance. Without using Redis’ AUTH that means anyone can access/change/delete your data. Be safe!