Trying to configure a PPTP Client interface as a default gw for specific IPs

RouterOS General
1

Hi,
I’m trying to setup a VPN client as an alternate Default Gateway for a few IPs in my network, mainly for streaming.
I have configure the PPTP interface without issues, it connects to the server and remains connected.

name="PPTP-Client" max-mtu=1450 max-mru=1450 mrru=1600 
      connect-to=my.vpn.server user="thisismysecretuser" 
      password="mysecretpassword" profile=default keepalive-timeout=60 
      add-default-route=no dial-on-demand=no allow=pap,chap,mschap1,mschap2

I have setup the NAT MASQ rule and the Mangle Prerouting rule for the routing marks for the src IPs.

;;; PPTP
      chain=srcnat action=masquerade out-interface=PPTP-Client log=no




chain=prerouting action=mark-routing new-routing-mark=PPTP  
      passthrough=yes routing-mark="" src-address=10.10.10.51-10.10.10.60 log=no 
      log-prefix=""

I’ve also setup the routing table that will route the marked traffic of the specific src IPs.have

#      DST-ADDRESS        PREF-SRC        GATEWAY            DISTANCE
 0 S    0.0.0.0/0      				        PPTP-Client              1

I can see the traffic going out but not coming back, there seems to be an open route and I just cannot find what the problem, any suggestion is appreciated.