check your fstab
the mount sources could read
/dev/mapper/dataX
OMV does some mapping behind
check it with ls, try to mount them manually
if successful then check the non-working (in your case) fstabfor example with
ls -l /dev/disk/by-label/
here:
lrwxrwxrwx 1 root root 10 Dec 18 09:32 WDred5p3T -> ../../dm-0
which points to the first luks device dm0
Here it works. I decrypt the drive after boot via the web. Then reread the shares via the MiniDLNA-refresh, restart Docker
Maybe you have to do a mount -a after unlocking manually if you find no fault in your fstab.