No access to SMB sharing on Windows Server 2019

I am new to Windows Server.
I’m trying to create an SMB share using the Server Manager tool on a Windows Server 2019, but unfortunately no matter what I do, I always get an error message. It comes the login window, enter the login data. This data is not accepted although I can login with it in RDP. The user also has full access. On the client I try to access it with win.example.comdownloads.

What could be the problem? Where could I have missed something?