I found a workaround here: https://askubuntu.com/questions/915549/16-04-cifs-host-is-down-but-they-are-not
I got there because trying to mount it from the command line with “mount.cifs” gave me a “host is down” message.
Manually adding “vers=1.0” at the end of the fstab entry allowed me to mount the share again.