Could you elaborate a bit on "labels on the dashboard with no data in it"?
Could you post a screenshot of how it looks?
Loos like you have 5 distinct datasources, correct? Are all of them extracts? Are you using blending?
If you setup the extract schedule when you published the dashboard, tableau will try to refresh every data source in the workbook.
This means that tableau is going to try and find the 4 excel files and query them to refresh them. If you just use the file navigator to select those files, you likely just have a local machine path. Something like C:\Personal\<USERID>\Documents\Tableau Projects\Viz of the Day\file.xlsx
Tableau server likely won't have this same file path and file available, therefore the server won't be able to refresh the extracts. Causing the extract refresh to fail for all of your data sources.
To solve for this, your best option is to publish the 1 sql server data source as a tableau data source. Then replace the orginal sql data source with the one you just published to the server. (i recommend keeping a backup file for the data source so you can make changes later if you need to.) Then you should schedule the extract refresh just on the sql server source and not on the workbook.