First, what macOS version are you running, and what is the version of Debian that you're running in the VM.
Did you check the network status from within the virtual machines and not just rely on ssh.
Do you have your Mac configured never to sleep? It's problematic to allow the Mac to sleep while VMs are running.
From the last time that you used the VMs successfully:
Have you shut down the VMs, then restarted your Mac.