It seems that you are caught in an authentication loop this is usually caused by the fact that the Tableau Server Run As User is not able to access or find a valid saplogon.ini file that is required to connect to an SAP BW server.
You can find more information in the link below
SAP Credential loop
Did your tableau administrator give you the rights and needed privileges?
secondly check the options in the links given below,it may help you out.
- Error Message: "To open this view, you must sign in to the database that the view uses" When Viewing Workbook Published …
- Error "To open this view, you must sign in to the database that the view uses" Opening Published Workbook | Tableau Soft…
- To open this view, you must sign in to the database that the view uses.- SAP BW datasource
- Avoiding Database Login Prompt in Tableau Web... | Tableau Love