Can not reach samba server on Ubuntu

I’ve a 18.04 Ubuntu client. Installed samba on it with the config:

[global]        workgorup = WORKGROUP        server string = file server        log file = /var/log/samba/log.%m        max log size = 1000        encrypt passwords = true        invalid users = root        socket options = TCP_NODELAY        security = user        unix extensions = yes  [Serien]        comment = Serien        browsable = true        writeable = true        path = /srv/Serien        read only = no        valid users = smbuser 

When I execute testparm I got the result: Result of testparm

Windows workgroup is equal to the config: WORKGROUP

Status of the samba service is: Status of samba service

Before I installed gitlab, the samba share still worked. After the installation it didn’t work anymore.

Do you have any ideas?