Can't schedule refresh on Excel Workbook because the data sources don't support refresh

I have set up an Excel Workbook with two tabs and a table in each. The content is populated into the table by hand/typing directly into the table. There are no other external data sources populating the table. However, when I try to schedule a refresh to the workbook, I get the following error message.

You can't schedule refresh for this dataset because the following data sources currently don't support refresh:Learn more about data sources that currently support refresh.

That links to a page "Use personal gateways in Power BI." The Excel Workbook is saved on SharePoint via a Teams channel/files.

This is the only message, and I have no other way to troubleshoot the issue that I can see. Is there any other diagnostics I can run on the workbook to determine why I am unable to schedule the update? I can't rely on stakeholders to refresh the data manually.

Thank you.