Wireguard server and/or iptables issue [SOLVED]

[erg_samowzbudnik]

I'm setting up wireguard server on a remote RPi to connect to with a laptop. Both run Gentoo. I can already reach the wireguard server (tcpdump shows a packet arrive) but then connection instantly dies on a client and I need to 'wg-quick down wg0' to get network back (on the client).
RPi runs iptables. So perhaps I'm having an issue with its' rules? I am not too good with networking/iptables so I've been trying to copy/paste rules into /etc/wireguard/wg0.conf ... I've tried with none, explicitly opening port used by wireguard as well as each of those two sets below:

PostUp = iptables -A FORWARD -i wg0 -j ACCEPT; iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
PostDown = iptables -D FORWARD -i wg0 -j ACCEPT; iptables -t nat -D POSTROUTING -o eth0 -j MASQUERADE

PostUp = iptables -A FORWARD -i %i -j ACCEPT; iptables -A FORWARD -o %i -j ACCEPT; iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -D FORWARD -o %i -j ACCEPT; iptables -t nat -D POSTROUTING -o eth0 -j MASQUERADE

but connection still dies as soon as I bring up wg0 on the client.

Edit:

servers' /etc/wireguard/wg0.conf

[erg_samowzbudnik]

The issue was resolved by setting net.ipv4.ip_forward=1 in /etc/sysctl.conf