Scheduled Refresh Data source credentials

Yes, if a Standard Gateway is already installed on prem then the Tenant admin needs to add it and add you as a user in the service. Once done the you will be able to add your source to the gateway and connect your semantic model

Hi juststarting ,

Because your data source is on-premises MSSQL Database, you need to install and configure the Standard Mode Gateway in your local machine, please confirm the gateway could access the Database successfully, then you need add a data source for gateway in Power BI Gateway Portal, then you could set the gateway and connection in the semantic model settings, then you could refresh this semantic model.

For more details, you could read related document: Manage a SQL Server data source - Power BI | Microsoft Learn 

Best regards,
Community Support Team_Binbin Yu
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

Update to original post.  Our IT had already set up the on site organisation Gateway, they had also added me onto the Gateway but Refresh was still failing, so the Gateway was not the issue.  On reports, I had added in SQL script that I had previously written in SQL Management Studio as Power Bi could not give me the links I required.  I noticed that when I clicked onto the created tables, the View Native Query was greyed out, so "Folding" was not occurring.  Searched on Youtube and was able to find several solutions to this, ie to activate View Native Query.  Once this was done, re ran report in Desktop to ensure still working, then Saved and re published report.  In Service was then able to complete a successful Refresh and scheduled Refresh.  Thank you to everyone who tried to assist with this, much appreciated