Sounds like it's an issue with your VLAN/Trunking configuration. As per earlier comments, post a more technical view of your environment/Network diagram.
My assumptions by your post that you've not added the VLANs to your MX device or that the downlink from the MX to your internal LAN has not been setup as a Trunk with the two VLAN's allowed over it.
Eliot F | Simplifying IT with Cloud Solutions
Found this helpful? Give me some Kudos! (click on the little up-arrow below)