omv4版本虚拟机web问题

OMV4 is end of life. Same for Debian 9 which is the basis for OMV4.

You should reinstall using OMV5 which is based on Debian 10. However, there is no virtualbox plugin for OMV5 anymore. You have to install virtual box along OMV on Debian, or use cockpit to set up virtual machines based on KVM/QEMU