Why can't Windows 10 see the local network behind Mikrotik?

Question

VPN

On Ubuntu, vpn l2tp is raised, mikrotik acts as a client and behind it is a local network. From the ubuntu server, I see Mikrotik clients, but from the windows client, I don’t see Mikrotik clients, can anyone tell me about the routing?
ip address of mikrotik 192.168.42.10,
ip address of ubuntu 192.168.42.1,
network behind mikrotik 192.168.88.1-255
commands are registered on ubuntu server

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
ip route add 192.168.88.0/24 via 192.168.42.10

Mikrotik has the following routing settings
on Windows: