Credentials are invalid public cloud Sharepoint online-PowerBI.com connection

Similar issue except I'm using an Excel spreadsheet that is stored in a SharePoint Online document repository.  When I did the initial Get Data to access the spreadsheet, I had a hiccup with either SharePoint or PowerBI inserting a "@SSL" into the file path - which prevented its upload, but when I deleted the "@SLL" from the filepath, I was able to bring in the data just fine.  People I have share the dashboards with can also see the visualizations just fine.  Now I go to schedule a daily refresh and it says my credentials are invalid.  In this case, it's using Windows credentials and I'm still logged in as the original Windows user I was at the beginning, so this is making no sense to me.

Having said that, I'm logged into a preview version of a PowerBI using different PowerBI credentials than my Windows credentials.  Could this be the problem?  If so, then why was I able to get the data in the first place?