Tailscale to pfsense forwarding to another site connecte

[glassy]

I have a dilemma: Customer refuses to use tailscale and doesn't have any convenient VPN access to his MS Windows server (in the picture - server on LAN B) so that our engineer who travels around the World with MS Windows workstation (W1 in the picture) could access the server over RDP .

Customer however is happy to provide an IPsec tunnel from his LAN B to our LAN A.

We have used pfsense (CA edition) for our router (router A in the picture) on which we have installed tailscale package and established an IPsec tunnel between our LAN A and customers LAN B.

Tailscale access from W1 to hosts on our LAN A is working (as one of the hosts advertises our LAN A and LAN B subnets for tailscale hosts) however not working over the IPsec tunnel to hosts on LAN B.

I wonder is there any way, configuring our pfsense firewall or installing some router on LAN A etc. so that we can have W1 access the server on LAN B?

Many thanks for any insights, suggestions or comments.

note - first we configured that LAN A and LAN B subnets were advertised by the pfsense router itself but later installed a separate host on LAN A which dos it. But still no connection to W1.