must be the one of those "oddballs" that use static IP as well as MAC address on my pfSense firewall/router to identify OMV. I also use static IP in OMV network settings. All is working fine.
I do roughly the same thing. I statically address my R-PI AND I set a static DHCP lease, at the router (or whatever is used for a DHCP server) for the same address. This associates a hostname with the static address for local name resolution. (A crude local DNS.)
I can't help but wonder what process the R-PI users in this tread are using to build OMV? Is it -> this one?