motdgot displayed (this is not important for you but for other people reading here). Which OS are you using normally? Windows? If so please open
ping raspberrypiand post the results.
The OMV Image for RPi needs Internet access on first boot to finish the installation otherwise you won't be able to access. Your symptoms indicate name resolution problems (DNS).
No more contributions to this project until 'alternative facts' (AKA ignorance/stupidity) are gone