need guidance on allowing a dialup vpn connection pass trough pfsense firewall

[shun5354]

initially i was setting up the pfsense as my testing firewall to propose for my company.
after successful install the base of pfsense and have also setting up internet connection to ISP.

after all LAN able to access internet with the base pfsense setting without any further done.

but i test to access VPN on 10 pc randomly, result are 4 successful connected but not the other 6 pc. all computer are confirm the setup are same setting.

any way to make sure all computer are able to successful dialup to our satellite location where the VPN server location.

hope to get guidance to resolve this issue. many thanks