HAve you given the NAS a static IP and done all the port forwarding?
are you accessing it http:// or https:// with the port as 5000 ?
Check under
Network
DSM settings
there is a flag to enable HTTPS access also - just in case your only trying http://ip:5000
I would create the NAT's directly on your router rather than via DSM - it never seems to work that well when I've tried to use it. The time it takes for it to fail - you could have set it up manually.
What version of DSM are you running ?
I would just create the NAT for what ever port you want to use to get to the DSM interface i.e 5000 on the router.
Take it your using that EZ-Internet app ?
Can do, its pretty easy to be honest as long as your comfortable with your router.
That EZ-Internet app is pants..
Ever since the bitcoin mining malware I just use a vpn in my router instead, I rather have one potential security hole in the router than hoping all services I have running on the nas are not wide open to attack.
Granted the router is an asus one so i'm probably screwed anyways.
The ports you need to forward are 5000 (http) and 5001 (https)
This link gives all the ports used:
https://www.synology.com/en-us/knowledgebase/faq/299
and the router config tests fail on 5000/5001/80 but 443 is fine 