VPN under Access Point Mode

Hi everyone, due to the topology of my network I have to use the Asus router in Access Point Mode and I can use the USB Apps like FTP, DLNA, etc... but the not the VPN, it disappear from the list. Is there a way to have access to it? Is there anyone with the same issue than me?

Thank you in advance,
David

PS: Sorry if this topic is already answered, I've tried to search for it and couldn't find any.