Hey,
I had similar problems.
I installed OMV via the installation-script. After completing without any errors my raspberry pi 4 wasn't able to boot.
SOLUTION:
Running the installation-script without the network setup.
from the Github Page:
wget https://github.com/OpenMediaVault-Plugin-Developers/installScript/raw/master/install
chmod +x install
sudo ./install -n
EDIT:
Aftern adding the wlan0 as an Interface via the web ui i ran into the same problem again. With a connected ethernet cable it still boots up!
So it seems that there is a problem with the network managment.