Refresh service dashboard with datasource being endpoint from on prem servers

Hey all,

I am using an endpoint that allows me to bring in data from an on prem data source that isn't connected to open internet. 
This works just find in powerbi desktop with manual refresh, but I cannot get it to work for my powerbi online dashboard. Refresh fails every time no matter what I do.

Issues I'm thinking it might be : this data source does not require credentials, also I've read elsewhere I might need to do the data gateway solution??

Can anyone help with this?

Thanks