Problems to connect with local SQL Server

Hello community,

I can not connect with a local SQL Server in Power BI Service.

The gateway responds with this error message:

The data source cannot be created.
Invalid connection credentials.

I want to use a SQL Server login, not a Windows login.

Connecting on SSMS with the SQL Server login works fine, but in Power BI Service it doesn't.

PS: It works with Windows Login, but I don't want to use that.

Any ideas?