Issue trying to route Cuckoo traffic through a VPN

Hi everyone, I’m trying to configure Cuckoo sandbox to route traffic through a VPN, however, I’m getting the following error:

<CuckooStartupError: The network interface that has been configured for VPN *** is not available.>

I have followed all the steps in the Cuckoo documentation to set up the VPN and have configured tun0 in both the VPN .conf file and in the rt_tables. Therefore, what is going on here and how may I fix it?