Cannot access devices when connected through OpenVPN

I’ve set up OpenVPN using this guide.
I’ve also added a firewall rule to allow port 1194:

/ip firewall filter
add action=accept chain=input comment=OpenVPN dst-port=1194 protocol=tcp

The problem is, when I connect to the VPN from the internet, i cannot ping any of my local machines (including the router on 192.168.88.1). However, when I connect to the VPN from inside the network, i can ping all machines no problem.

Does anyone have any ideas what i’m doing wrong?