Im trying to setup PPTP on an RF600 to support more than 1 concurrent user, but if 1 person is connected no one else can. Must I run it through a Radius server for this to work? Does an RF820 support more than one concurrent pptp logon?

The RF600 can support more than 1 PPTP user. It all depends on how you configure the PPTP pool addresses. If you have multiple PPTP users behind some NAT / firewall router and they are all trying to connect at the same time, then you will need to upgrade your RF600 to the latest 3.32 firmware.

The RF820 / RF830 does support Multiple PPTP connections (up to 15).