To check if TUN is enabled run the following command,

~# cat /dev/net/tun

If your output is,
cat /dev/net/tun: File descriptor in bad state
Then TUN/TAP is enabled on your VPS.

If your output is,
cat: /dev/net/tun: No such device
Then TUN/TAP has not enabled on your VPS.

You can enable TUN from the SolusVM Control panel.

Source: www.virtualizor.com/docs/admin/tun-tap/