Mobile Data stopped working
I had Data roaming issues with my Nokia 8.1 Sirocco phone, tried all avenues for answers, Telstra support, Nokia support, all resets and even tried a full factory reset but all efforts did not work. 

I sent my phone to Nokia in Sydney, they called me and told me phone was working there, I had to reset my APN protocol and APN roaming protocol. 

From settings &rarr; network &amp; internet mobile networks &rarr; advanced  &rarr; access point names and changed settings from IPv4 to IPv4 / IPv6, pressed the 3 dots top right hand corner and pressed save. 

It works  now again, hope this helps anyone with same issues.