Samba shares don't show up in file explorer

It's not possible for me to reach the samba shares by searching for samba shares.
But I can access the samba shares, when I directly point to the path of the samba share.
I tried on Debian, Manjaro, Windows 7 and Android. Everywhere it's the same.

What it's also interesting when I use the command
$ smbclient -L hostname -U%
my samba shares show up, but when I use the command
$ smbtree -b -N
my shares don't show up.

I hope somebody can help me!