I know that W10 has been a PIA for a number of users in respect of shares both visible and being able to connect to due various settings not being enabled.
Well it could be that a recent MS update has turned off Network Discovery! one of the options that requires to enabled.
I have never had a problem connecting to OMV shares from my W10 workstation, until today when a message came up telling me to turn on Network Discovery in the Network and Sharing Centre. Considering I have never turned this off since I enabled it quite some ago I can only surmise that this may have had something to do with KB4489868 the latest cumulative update in March.