I got the same problems on my OMV on raspberry pi, but I found a solution for now, which is working very well, until the openvpn (and the openvpnAS) will work gain in a decent way.
First of all, remove openvpn from OMV via web gui.
After that, go to the below link and follow the very easy setup explanation, based on a script:
http://peterjolson.com/super-e…config-on-openmediavault/
The script has been updated by that time, so the procedure is slightly different now (and even easier), because at the end you will get a file client.ovpn on the root (or [filename_you_choose].ovpn), which can be save and uploaded on you openvpn client (I am using it also on my phone and it is working very well).
Please keep in mind that in your router you will need to forward the VPN UPD port to your OPV ip address. Please also consider that the script will take a very long time to generate the keys, it is normal.
To save the client.ovpn, use the command: "scp client.ovpn your_username@remotehost.edu:/some/remote/directory"
Do not install or activate openvpn from openmediavaul web gui, otherwise OMV will overwrite the openvpn settings and it might make a mess.
I hope this will help, as it helped me!