I was having the same issue after installing 3.9.1 on a new machine and I had tried installing all the updates including the most recent test channel updates and it sill wasn’t working until I found this thread. I tried each recommendation one at a time and nothing worked (including systemctl restart nmb.service at first), and yum wouldn’t let me reinstall libwbclient-4.6.2, so I uninstalled it (only, I left the dependencies since there were many) and then installed it again, and while I was at it I ran yum clean all and then eventually something clicked and systemctl restart nmb.service finally fixed it.
After writing all that I see that I seem to have had the same issue as doenietzomoeilijk, with the SAMBA_4.4.4 not found popping up somewhere along the way. And now that I’ve read through and saw that it may have been caused by an interrupted update cycle, I may have rebooted during an update as well. I was booting off a really slow USB flash drive and it wouldn’t shut down, so I thought it had some issue and just turned the computer off after a few minutes and restarted, so that may have been what caused my issue as well, maybe?