Manchmal fehlt auch das forwarding.
Mir hat das geholfen:
Make sure you create the following file using a text editor too:
# vim /etc/sysctl.d/10-wireguard.conf
Add the following text:
Reload all changes and turn on NAT routing:
# sysctl -p /etc/sysctl.d/10-wireguard.conf
# chmod -v +x /etc/wireguard/helper/*.sh
# systemctl restart wg-quick@wg0.service