I finally got it to work. I used the Use OneDrive & SharePoint activity with a Modern Upload Files. On the OneDrive and ScorePoint (under Classic), I chose Use Integration Service for my unattended bots account. Then on Upload Files I selected that account again. To use the modern Upload Files I had to convert my file string to iLocalResource, then to iEnumberable , following this post.
Still unsure why I can no longer use the application ID and secret that was set up in Azure last year. This, however is working for now.
