My node is 20 days old, is it normal to have little traffic?

I’m guess you mean VPS.
If you node online, not suspended and not disqualified, it working fine.
However, since you have problems like

and

I can assume that it was mostly offline. Please, fix the issue.
By the way, if you use a VPS only for Storj it’s probably not worth it - you will pay more than your income, you can use this Earning Estimator to have an idea:

If you mean a VPN (virtual private network) and not a VPS (virtual private server), then only a few VPN providers give you a port forwarding feature: portmap.io, ngrok, PIA, PureVPN, etc.
If your VPN doesn’t have a port forwarding feature - the node will be offline, especially if you do not have a public IP (your WAN IP is different from the IP on Open Port Check Tool - Test Port Forwarding on Your Router).