Remote User VPN can't access site-to-site VPNs

The scenario is, 5 sites with each their EdgeRouter.

Each one is connected, thru WAN, via IPSEC site-to-site VPN.

It is workinf flawlessly, hosts in site X can ping hosts in site Y.

One of the sites has, besides the site-to-sites, a remote user L2TP VPN, authenticating with a RADIUS server.

That is, also, working fine. However, the remote users can only access the site, from which the L2TP server is running.

What rules must I add, to allow the remote users, vpn'in with L2TP, to also reach the sites interconnected with the IPSEC tunnels?

Thanks in advance.