Internal Access Issues

External access mode is disabled

The usual cause for that is incorrect or slow updating DNS from ISP.

Check DNS info from the machine you are trying to access your device with nslookup command line tool:

nslookup [device name].syncloud.it

If you see incorrect IP

You may want to switch your DNS server to 8.8.8.8 (Google DNS)

Test it first:

nslookup [device name].syncloud.it 8.8.8.8

If you see timeout message

Probably your router does not allow DNS which points to a local IP.

Fritzbox for example allows to add an exception: https://en.avm.de/service/fritzbox/fritzbox-7390/knowledge-base/publication/show/663_No-DNS-resolution-of-private-IP-addresses/

Phone DNS issue

Install DNS app DNSDig on Android or Deep Dig on iPhone

Enter your domain name and if get IP. This will tell you if your local DNS provider is good or if you need to switch to 8.8.8.8 (dns.google) for example.

If you do not know how to switch DNS on your phone google can help you.

External access is enabled

The main reason usually is a missing Nat Loopback feature on the router, more info: Nat Loopback