DrayTek 2862 to 3900 VLAN VPN not Routing

Hello

I have a DrayTek 2862 with a single LAN behind it.
I also have a DrayTek 3900 with several LANs on VLAN behind it.
I need to route a VLAN through a VPN to the 2862.
I have set-up the VPN and routed to the relevant subnet, but see no return traffic.
I have done this before with the same router without issue, but cannot get the traffic to route through this time.
The traffic is sent at each end, but nothing returns.
There is no VLAN at the 2862 end.
Obviously the traffic is not being tagged through the WAN as it would just fail.
I cannot see what is preventing the flow of traffic, any suggestions?

This is some kind of incompatibility with the DrayTek 2862 as I have performed this many times with two 3900/3910 routers. The DrayTek 2862 does not seem to understand the VLAN at the other end of the tunnel somehow.

We are going to replace the 2862 with 3900s to solve this.

Just to say that the issue was the 3900 to 2860 VPN compatibility. The 2862 lacks the selection of VLANs at both ends and the 3900 does not forward the packets correctly as a result.

I had thought it might be the switch not labelling the VLAN packets that was causing the problem, but discounted this.