Why doesn't my mobile app connect to the server?

Works fine on web browser on the mobile.
When I use mupx deploy --mobile-server it creates the APK fine.
After signing and running on my phone it does not load the account login or the ionic icons so I presume it does not connect to the server.
Are there any things I could have easily missed that would prevent it from connecting?

I have this in my mup.json, I’m not entirely sure if both are needed but I remember having a lot of issues when I first started and this is what I finished with in the end…

// Configure environment
"env": {
“ROOT_URL”: “”,
“DDP_DEFAULT_CONNECTION_URL”: “” // this is same as --mobile-server?

Didn’t have the DDP_DEFAULT_CONNECTION_URL, result was the same sadly

Do you have App.accessRules set in your mobile-config.js?

yeah it has App.accessRule(‘*’);

mup env is

“env”: {
“ROOT_URL”: “”,
“PORT”: 3000,
“UPSTART_UID” : “meteoruser”