Can't connect to pptp server in LAN of R1

I had bought a banana pi r1 and setup it as a router by VLAN as what instructed by the document(Bananian). However, my device in LAN can’t connect to PPTP server. I didn’t change iptables besides add “-A POSTROUTING -s 192.168.1.0/24 -o eth0.101 -j MASQUERADE” and open port forward. Could someone do me a favor~ orz

iptables as below

-P PREROUTING ACCEPT -P INPUT ACCEPT -P OUTPUT ACCEPT -P POSTROUTING ACCEPT -A POSTROUTING -s 192.168.1.0/24 -o eth0.101 -j MASQUERADE

-P INPUT ACCEPT -P FORWARD ACCEPT -P OUTPUT ACCEPT

cat /proc/sys/net/ipv4/ip_forward 1

I’ve no experience myself with PPTP, but did you try the following pages : https://www.domoticz.com/wiki/Installing_a_PPTP-VPN_server_on_a_Raspberry_Pi

thx:) however, the problem I met is that the device in LAN can’t connect to a remote VPN server. I didn’t setup a VPN server on R1

btw, the problem I met suddenly get fixed. I didn’t do any thing and it just work~