LAG port goes BLK DIS state after adding to VSTP

Hi,

I have a VSTP running between a virtual chassis (2 x QFX5110) and Cisco VSS (2 x Catalyst 6509E), the Root Bridge is on the Juniper VC and the LAG between them works just fine.

I wanted to add another Cisco switch to the Juniper VC, so I created another ae14 LAG, added ports to LAG and when I add the ae14 port to the VSTP configuration (not even attaching cables) it automatically goes into BLK (Blocking) DIS (Disable) state. Even after I do cabling it stays in that state making the LAG not working at all.

What I do wrong ?

This is my configuration of STP protocols on Juniper.

rstp {
    bridge-priority 4k;
}
vstp {
    bpdu-block-on-edge;
    interface ae0;
    interface ae14;
    vlan all {
        bridge-priority 4k;
    }
}

And this is when I added ae14 to config.

john@core-vc> show spanning-tree interface

Spanning tree interface parameters for VLAN 10

Interface                  Port ID    Designated         Designated         Port    State  Role
                                       port ID           bridge ID          Cost
ae0                          128:3        128:3   4106.d007ca44b990         1000    FWD    DESG

Spanning tree interface parameters for VLAN 14

Interface                  Port ID    Designated         Designated         Port    State  Role
                                       port ID           bridge ID          Cost
ae0                          128:3        128:3   4110.d007ca44b990         1000    FWD    DESG
ae14                        128:17       128:17   4110.d007ca44b990        10000    BLK    DIS

Not all VLANs which are on ae0 are on ae14 that is why ae14 is not showing up on VLAN10 for example.

Why ae14 is getting blocked ?? (Without even cabled).