I enabled the PPTP server, but I cannot pass traffic into my internal networks
| PPTP is no longer considered a secure VPN technology because it relies upon MS-CHAPv2 which has been compromised. If you continue to use PPTP be aware that intercepted traffic can be decrypted by a third party, so it should be considered unencrypted. We advise migrating to another VPN type such as OpenVPN or IPsec.
More information on this can be found at https://isc.sans.edu/diary/End+of+Days+for+MS-CHAPv2/13807 and https://www.cloudcracker.com/blog/2012/07/29/cracking-ms-chap-v2/
Firewall rules must exist to allow this traffic.
Navigate to Firewall > Rules and add a rule on the PPTP tab to permit traffic from PPTP clients. (ex: interface PPTP, protocol any, source PPTP client subnet, destination any)
Once appropriate rules are in place, traffic will pass through the interface correctly.